I'm honestly not sure I think Apple will ever bring out a foldable. There's just something about that kind of format, I think it's just too finicky for their brand. I think they'd rather polish their ecosystem where they spread the functionality out between watch, phone, tablet and computer to where they can claim that setup will satisfy any use case better than a foldable. Just a hunch that that's what they prefer to focus on.
For me personally, there are moments when the Fold intrigues me and I want one. But at the end of the day, what I'm really looking for is a small, super pocket friendly gadget that does the in-the-moment stuff for which you need a device that's ready to be pulled out at any moment, and a tablet small enough to be brought along almost anywhere. At the end of the day, I think I'm honing in on a iPhone 12 Mini/SE size phone + an iPad Mini (cellular version) after they've updated it to iPad Pro design.
Honestly, that size iPad I can already bring anywhere it needs to go, even if it doesn't fold. And if I'm out and about without any bag of any kind, a Fold wouldn't be comfortable to bring in my pockets anyway. And for any quick, in the moment tasks like quickly snapping a shot or buying a ticket while the bus arrives, a tiny device like an iPhone Mini will be much less of a hassle to use than a brick like the Fold.
Sure, you can make the argument that foldables will evolve until they're as thin as a phablet size phone is today. But honestly, I think that's more than a few years off. Not only do batteries need to shrink until they're wafer thin, they need to do so while still being safe. And that'll be no mean feat with a gadget that thin. In fact that goes for the construction as a whole. Half the thickness of an iPhone 12 Pro Max is 3.7 mm. I don't see a device getting that thin without breaking every other day, with display malfunction and exploding batteries as a result, for quite some time yet. Like, we might seriously reach holographic projection devices like in sci-fi movies sooner than that.
Roll-out displays and other kinds of folding/expanding designs? Too finicky, I don't buy any of those honestly.
Meanwhile, Apple will keep focusing on their Holy Ecosystem with a group of devices that will get individually slimmer and more flexible and powerful so that they get easier and easier to bring along, while also getting easier to work "across" as it were. While of course continuing to market exactly that setup to keep people's eyes away from foldable solutions. I'm not saying that is better, but that's how I see them approaching this.
Tl;dr, I'd love a foldable that's as thin as my 12 Pro Max when folded and doesn't have a crease when unfolded, while also being durable enough for daily, non-finicky use, but I don't see us getting there for a very long time yet. And I don't think Apple is worrying about taking part in that race, at least not for also a very long time; if ever. The Fold series might drop in price and move gradually from niche to something at least a bit more mainstream, but not enough for Apple to really start worrying about it. IMO.
