So I will come across as an obvious hypocrite. I like to see innovation but at the same time I am skeptical of the cost benefits and reliability. As a general rule I go for version 3 where version 1 has major flaws the designer could not spot due to their personal faith in their own “genius”, version 2 fixes the obvious issues, then version 3 fixes the less obvious issues.
So I own a 1" phone, 6.5" phone, a 8.4" phone and a 10.8" phone. The 10.8 has a detachable keyboard on a full 180" hinge. Each has their pros/cons. the 6.5" phone pro is it fits in my pocket but in many cases I still find it too heavy / bulky. The 1" is on my wrist, it suffers from battery life as its battery size is roughly 1/10th that of the other devices, text input is painful, but very easy to keep with me. The 8.4" allows for two thumb typing and better speakers, the 10.* has the keyboard.
The issue with all these folding devices is they worsen at least one thing to get that bigger / 2nd screen. The obvious in version 1 is cost and reliability. But even at version 3 you’d have either pocket size, or battery life issues as when that 2nd / folded screen isn’t needed its either adding bulk or taking space from something else such as battery capacity. So long as cost is high before version 3, I can own and use multiple devices each of different size, e.g. the 8.4" phone cost me $300 and I keep in my bag so whenever I am with more than just my pockets I have a non-folding bigger phone without sacrifice.