I live in an ancient city, in a medium-old apartment--one that is rapidly approaching its bicentennial. Like any building in continuous occupation for nearly 200 years, form and function have changed: it's been retrofitted with indoor plumbing, gas central heating, electricity, broadband internet. The kitchen has shrunk, a third of it hived off to create a modern (albeit small) bathroom. The coal-burning fireplaces are either blocked or walled over. Three rooms have false ceilings, lowered to reduce heating costs before hollowcore loft insulation was a thing. What I suspect was once the servants' bedroom is now a windowless storeroom. And rooms serve a different function. The dining room is no longer a dining room, it serves as a library (despite switching to ebooks a decade ago I have a big book problem). And so on.
But certain features of a 200 year old apartment remain constant. There are bedrooms. There is a privy (now a flushing toilet). There is a kitchen. There is a living room. And there is a corridor.
This apartment was built around 1820, for the builder of the tenement it's part of: he was a relatively prosperous Regency working man and his family would have included servants as a matter of course in those days. And where one has servants, one perforce has corridors so that they may move about the dwelling out of sight of the owners. But it was not always so.
Rewind another 200 years and look around a surviving great house, such as Holyrood Palace, also in Edinburgh. Holyrood largely dates to the 16th and 17th century, and reflects the norms of that earlier era, and if you tour it one thing is noteworthy by its absence: corridors. The great houses of that period were laid out as a series of rooms of increasing grandeur, each leading to the next. Splendid wide main doors in the centre of each wall provided access for nobility and people of merit: much smaller, unadorned doors near the corners allowed servants to scuttle unobtrusively around the edges of the court. Staircases ascended through grand halls at the centre of such houses (accessible from doors leading to the main function rooms around the periphery): servants' areas such as the kitchen, stores, and pantry might boast their own staircases, and the master apartments of a great house had their own stairs leading to privy or ground floor.
But the corridor in its modern, contemporary sense seems to have started out as a narrowing and humbling of the grand halls and assembly rooms of state, reduced in scope to a mere conduit for the workers who kept things running--before, of course, they later became commonplace.
My apartment is laid out around an odd, V-shaped corridor, with two arms: one leads to the kitchen, bathroom, store rooms, and front door, while the other leads to the dining room and living room. Bedrooms open off at various points: the front door is at the point of the 'V'. (I speculate that the intent was to keep the smells of cooking, smoke, and privy as far away as possible from the dining and living areas commonly used by the owner and his wife and children.) By 1820 the corridor had become an unremarkable space around which homeowners were now structuring their lives. The older style of tenement, focussed on a windowless central room off which all other rooms opened, still existed but was becoming rarer.
In the UK, the average dwelling is 75 years old. In other countries, they are considerably younger: in Germany homes depreciate after first sale, while in the US, they typically require extensive structural renovation or rebuilding after 30 years (continental climes are prone to greater environmental extremes). In Japan it's normal to demolish a house and rebuild from scratch on the newly cleared just-purchased ground.
And new homes reflect the needs and values of their owners.
It's unexceptional today to come across an open-plan apartment, because (except for the very rich) we don't typically share our homes with servants, and we have efficient ventillation and climate control. Try to imagine living in an open-plan Victorian flat with a coal-burning kitchen range and fireplace puffing out smuts, a maid and a cook to keep on top of the grime and the food preparation: it doesn't work. Try, also, to imagine a contemporary home without a living room with a TV in the corner. Go back to the 1950s and well-designed homes also had a niche for the telephone--the solitary, wired communications device, typically bolted to the wall in the hallway or at the foot of the stairs, for ease of access from all other rooms.
But today telephones have collapsed into our pocket magic mirrors, and TVs are going in two directions--flattening and expanding to fill entire walls of the living room, and simultaneously shrinking to mate with our phones. A not-uncommon aspect of modern luxury TV design is that they're framed in wood or glass, made to look like a wall-hanging or a painting. The TV is becoming invisible: a visitor from the 1960s or 1970s might look around in bafflement for a while before realizing that the big print in middle of the living room wall is glowing and sometimes changes (when it's in standby, running a screensaver). Meanwhile, microwave ovens and ready meals and fast food have reduced the need for the dining room and even the kitchen: to cook a family dinner and serve it in a formal dining room is an ostentatious display of temporal wealth, a signal that one has the leisure time (and the appliances, and the storage for ingredients) to practice and perfect the skills required. The middle classes still employ cooks: but we outsource them to timeshare facilities called restaurants. Similarly, without the daily battle to keep soot and dirt at bay, and equipped with tools like vacuum cleaners and detergents, the job of the housemaid has been shrunk to something that can be outsourced to a cleaning service or a couple of hours a day for the householder. So no more cramped servants' bedrooms.
The very wealthy ostentatiously ape the behaviour of the even richer, who in turn continue the traditions they inherited from their ancestors: traditions rooted in the availability of cheap labour and the non-existence of labour-saving devices. Butlers, cooks, and live-in housemaids signal that one can afford the wage bill and the accommodations of the staff. But for those who can't quite afford the servants, the watchword seems to be social insulation--like the dining room at the opposite end of the corridor from the kitchen.
The millionaire's home cinema, in an auditorium of its own, is the middle class TV in the living room, bloated into an experience that insulates its owner from the necessity of rubbing shoulders with members of the public in the cinema. Likewise, the bedroom with en-suite bathroom insulates the occupants from the need to traipse down a corridor through their dwelling and possibly queue at the bathroom door in the middle of the night.
Types of domestic space come and go and sometimes change social and practical function.
The coal cellar is effectively dead in this era of decarbonization and clean energy, as is the chimney stack. Servants' quarters are a fading memory to all but the 0.1% who focus on imitating the status-signaling behavior of royalty, although they may be repurposed as self-contained apartments for peripheral residents, granny flats or teenager basements. The dining room and the chef's kitchen are becoming leisure pursuits--although, as humans are very attached to their eating habits, they may take far longer to fade or mutate than the telephone nook in the hallway or the out-house at the end of the back yard.
Likewise, outdoor climate change and indoor climate control are changing our relationship with the window. Windows used to be as large as possible, because daylight lighting was vastly superior to candlelight or oil-lamp. But windows as generally poor insulators, both of sound and heat, and indoor lighting has become vastly more energy efficient in recent years. Shrinking windows and improving insulation (while relying on designed-in ventilation and climate control) drive improvements in the energy efficiency of dwellings and seem to militate against the glass bay and big sash windows of yesteryear.
My dining room turned library is both odd (most people don't have thousands of books) and obsolescent (books need not occupy huge amounts of physical shelf space these days). But other emergent habits require considerable space. Consider virtual reality games. A couple of years ago I got to play with a friend's Oculus Rift setup. VR games take up considerably more floor space than the wide-screen PC or console gaming they may eventually replace. (You need room to move about physically without tripping over cables or stumbling into furniture.) Even a high-end gaming PC takes up a lot of space: a custom chair with controllers, a stand supporting two or more wide-screen monitors. Today's TVs and monitors may be flat but they're nevertheless enormous. (Back in 1998, the last tube TV I bought boasted a then-large 24" diagonal screen. Today, the 42" screen in the living room feels subjectively small.)
I don't see some of the basics changing. In the absence of teleport booths we still need staircases, doors, and (in some cases) elevators. We're going to continue to need somewhere to sleep for the foreseeable future, and we're also going to need somewhere to deal with our excrement and personal grooming/hygeine needs, even if we all abandon home bathing tomorrow in favour of a surprise renaissance of Roman-era communal baths. I don't see clothing becoming much more disposable than it already is (I'm wearing a £6 tee shirt, thank you, but there's a £250 coat hanging by the door, that's in no way disposable, and I'm no fashionista), so we're still going to need wardrobes, albeit some of us more than others. Parking garages are still useful even if you don't own a car--for storage, for home freezers, for washer/dryers--although stand-alone ones in this part of town are increasingly being repurposed as the ground floor of small houses, and it's possible that the era of mass public automobile ownership will come to an end within my lifetime.
Anyway, this is a brain dump of some thoughts leading up to this question: what is the home of 2119 going to look like? (Assuming no collapse of technological civilization, and an orderly--and complete by 2119--migration to renewable energy sources. Also assume availability of synthetic fuels for air/space/sea travel, reasonable improvements in electrochemical batteries, and wholesale infrastructure improvements at least as extensive as post-WW2 reconstruction in Germany and Japan. And, come to think of it, a population plateau and demographic transition to gradual managed shrinkage and aging: let's peg global population in 2119 at stabilizing at the same level as it is today, without extensive genocide.)
Bear in mind that it's probably newly built since 2019. 80% of humanity lives within 200km of the sea; ocean levels are rising and extreme weather events are getting worse, so our cities will over time recede inland from the current coastline. An ageing, shrinking population is midly deflationary and means a likely surplus of housing after peak humanity: but also accommodations for frail/elderly people.
Today's millennials will have mostly passed away, the aged in this era will be the generation born after 2019. They'll have grown up with ubiquitous social media and broadband communications, with VR and AR as a given. They may relate to private automobiles the way we relate to butlers and maidservants, while finding something else we can't imagine entirely mundane. I suspect there'll be more communal living (but I could be wrong). Transport is going to be very different--if nothing else, there's no call for burning dead dinosaurs to set a couple of tons of steel and plastic in motion to move one person, let alone to devote 90% of our urban landscape to providing priority space for automobiles. This, in combination with climate change, suggests to me the end of American-style suburban sprawl and a trend towards much denser urban habitats. Logistics are also going to be ... interesting: neither Amazon's delivery drones nor Musk's hyperloop are really practical solutions in cities, while stuff like micromobility platforms (scooters, ebikes, segways, autonomous robot parcel carts) mesh with trams (streetcars), trolleybuses, and autonomous minicabs and vans.
The bedroom, wardrobe, bathroom, and some type of food storage/preparation area, aren't going away. Other spaces will also be around, and social/spatial insulation will be in demand. At the high end, the elite (whoever they are) will try to ape the living arrangements of previous century's elites, as a status signal if nothing else.
What else is conceivable? What am I missing that should be as obvious as the multimodal shipping container in 1950, or photovoltaic panels on house rooftops in 1990?