I wouldn't mind foldable phones having two separate screens with a minor gap between them - you'd avoid getting an ugly growing crease over time like with the current screens, and with a proper hinge design you could make them thinner too probably
There are already a few folding things like that on the market but they're not as popular. People seem to put up with the crease more than they're prepared to put up with a gap. Mostly because with a crease you can still have a full tablet like experience.
I was thinking about phones, having a "flip phone" without a crease which is "normal size" when opened would be cool. For tablet use the gap admittedly sucks
This bothers me a bit because I absolutely love my current gen horizontal fold phone. The crease isn't ugly or growing in the year or so I've had it. You can feel it, but I got used to that in days.