What I’m really looking forward to are outright foldable
In many ways, foldability is just the medieval substitute for a dynamic display. Instead of switching screens, you flip pages. Instead of zooming maps, you unfold the whole thing, then fold over everything except the part you're interested in.
I don't think foldability is just a medieval thing. People want screen real estate. They want to see their photos and videos in a large form factor. They also want to carry the screen in their pockets or backpacks. Foldable paper is a neat idea that achieves both. I would find it rather frustrating if I could only zoom into small parts of a map and never view the whole terrain in its 40-inches-across, 60-degrees-of-angular-diameter glory. Size matters.
Scrolling and zooming are not appropriate substitutes for folding in electronic displays. A real substitute would be a pocket-size device that can project an image of arbitrary size in mid-air, so that people can see their maps IMAX at a distance of 3 feet if they want to.
I don't think foldability is just a medieval thing.
I guess some people downvoted me because they took "Medieval" to be pejorative. I was being entirely literal. Linen-based paper was widespread in medieval Europe after the plagues. (Much of it was made of the linen clothing of people who no longer needed it, on account of their being suddenly dead.) Such paper is much more amenable to folding in the manner of a map than earlier technologies. (Though most everything seems to roll up into scrolls well enough.)
Scrolling and zooming are not appropriate substitutes for folding in electronic displays.
That's entirely contextual, as you also point out. You won't know how well things can take folding and how well the form factor performs in real life until you have such materials. Until then, we know zooming works. If I had something as light as and the same size as a clipboard that was daylight readable and yet as dynamic as an iPad, this would enable a whole other world of mobile applications that aren't quite there yet. I'm hard pressed to imagine an application I'd need that could fold out, which couldn't also be met by presentation/projection systems, or perhaps an interactive worktable form factor.
Take your maps example as a generic zooming vs. folding example. When you use something like Google Maps, if you set your browser window to show you 2cm x 2cm, would that be big enough, I doubt it. And yet your screen doesn't have to be as big as an unfolded traditional map, thanks to panning and zooming. This shows that a.) dynamic displays can reduce the need for folding but that b.) there will always be a (subjective) question of what works best.
As to a more realistic example - as a kindle reader, I wouldn't want a screen smaller than it already has, no matter how much zooming or scrolling it offers. And while the device can fit in a pocket, I generally don't like having it in one. If it was half the width and I could fold it in half, I would love that.
In many ways, foldability is just the medieval substitute for a dynamic display. Instead of switching screens, you flip pages. Instead of zooming maps, you unfold the whole thing, then fold over everything except the part you're interested in.