Folding LCDs have been a solution in search of a problem for years. Maybe they looked cool in some ID rendering or model, but I’ve never understood why anyone would want one other than the novelty factor. And as has already been pointed out, they’re destined for failure at the fold.
Yes, twice the screen, but also double the thickness, at least for the LCD and some supporting components. Figure on at least a few mm extra (LCD+touchscreen+case). I don't know of any material which can fold 180 degrees over and over, and not eventually succumb to fatigue. Maybe within the expected lifetime of a phone it will work under test conditions, but unless there is serious margin in the robustness, I would expect some to die at the fold in the real world, and that will never be good publicity.
