I work in usability, and participate in user experience sessions regularly. I've literally never seen anyone express frustration with the size of phones today. Ever. Well, except for many being unable to grip large phones properly and reach UI elements towards the top of the phone.That’s you. That’s not everyone. Just because you don’t see the appeal doesn’t mean countless others won’t as well.
You aren't going to get a foldable phone from Apple that turns into a tablet... for your pocket, probably ever, but especially until folded up it can be as thin as phones are today.
Other manufacturers rush to fads and gimmicks, but Apple isn't going to make this mistake. So keep dreaming.