Why? Display cost isn't a big deal any more. Display size is getting insane. I was in Costco yesterday. 70-inch TVs for $1500. TV sets are now outgrowing standard houses.

Solar cells already cost less than their installation cost as a retrofit on houses.

Not, "there's my workstation and the giant LCD monitor is no longer a status symbol" but more like "well of course the wall next to my bed is a star trek style all-walls-are-misterhouse interface to everything"

Not, "there's my solar panels which cost more than the roof they're sitting on although they are quite profitable" but more like "well of course every surface exposed to the sun charges a battery or sells electricity to the local power co-op".

Think of the weird stuff that'll happen culturally. Campaigns to save the topsoil because people who want $$$ more than they want grass lawns will kill their lawn by shading it with cells. Endless arguments on HN about if you're better off selling solar power to buy hot pockets or using the sunlight directly to grow lettuce. All battery powered rechargeable devices will charge when sitting in the sun, so you'll have interesting social patterns about not stepping on or running over people's devices. When sunlight equals money you'll have people chopping down their neighbors trees illegally on a regular basis. They'll be a short term "vegas" effect where every surface of the world will have to be covered with gaudy advertisements. People will wear clothes that are computer display fabric and download new patterns more often than they wash, probably. And they'll be viruses that eat your electricity until you pay them off, throw spam on your epaper, and upload nude texture packs to your ecloth clothing (although, who knows, maybe people will intentionally like that?)

I'm old enough to have lived thru long distance voice communication going from "too expensive for regular folks per minute" to too cheap to meter. I can see something coming for at least low power electricity and computer display tech.

Also, imagine putting high-dpi full-colour displays on all your walls and ceilings, so that one can change wallpaper at the flick of a button, or place ‘paintings’ wherever one wants.

Backlit LCDs would lead to uncomfortable living; rooms would be warm, there would barely be any shade in the room, and power costs (even if solar cells are cheap as paper) would probably be high.

e-ink wins on the power usage front, and is reflective, rather than backlit.

No. Not going to happen. The wall, the plain white-ish surface, has been a thing for thousands of years. I own a nearly infinite number of nails, glues and other fasteners to affix thing to my white walls yet change the appearance of my walls ... well basically never. It would be moderately cool to see a wall capable of HD television, but the physics of ever doing, in comparison to a dedicated device, will never be practical. There will always be a place for paint.

I for one would love having every inch of my interior walls e-ink, changeable on a whim, and would likely pay $1 to download a new wallpaper/design on a regular basis.

People will pay extra for wallpaper that doesn't move.