Phones that cost from 1,1ke to 1,7ke are coming "mainstream"? Yeah, right. I wouldn't mind a foldable phone if the screen could actually handle it, it would be light and thin enough to actually carry around with you (and not the thickness of two phones glued together), and if the price was right. Currently none of those are even close to being reality.
But yes, given that they took care of all that I'd love to buy a device that'd work as an iPhone and would double as a iPad Mini when required. And no, I'm still not prepared to pay the price of an iPhone PLUS iPad mini for such a thing.