Umm, no thanks.
Personally, I think the Motorola RAZR v3i was the pinnacle of physical dimensions for a phone to the point that you could forgive the clumsy UI and the idiotic idea of using a keyboard that was so shiny that it made the phone unusable in sunlight (Chinese cloners were smart enough make it matte). It had the right weight, it had a swappable battery and it had an outside screen just informative enough to make it worth using. In short, from a pure size/utility perspective it was never bettered as a phone. Oh, and it was a true Motorola in that it had rather good reception despite its diminutive size - that has in the past overriden my concern about their UIs (remember the StarTAC flip?).
However, adding the folly of a solutions-looking-for-a-problem foldable screen with all associated consequences and problems will NOT enable a rerun, sorry. One display/touch screen for keyboard and one just screen, yes, interested, but not this.
The phones I buy tend to work for 3..4 years - I don't expect a foldable display to make it past year one, and that's even without considering that it will make the famous "flip" of that phone a lot less snappy to boot. Yes, I didn't mention price, the v3i was so good it even came in an expensive branded version and that too sold like hotcakes. When you get it right, those are the benefits.
No, thanks. In that case I prefer the original v3i then - crud UI or not.