The modern flip-phone
> whether foldables will become mainstream anytime soon? Unfortunately, the answer is no,
Why unfortunately? They are not a particularly good idea. I wouldn't buy one until someone can prove to me that the screen will be in the same state after ten thousand folds (in cold weather, with bits of grit wedged in the fold - as you'd get in your pocket) as it is when new.
Even then, what really is the point? It takes longer to access whatever you want to do and a screen that is twice the size is still pretty dam' small, yet with a greater area uses more power. And since it isn't as if the battery would fold, that will be constrained in size.