It’s likely that I will end up getting one of these, eventually.
I suspect all my apps will run OK on this. I have been designing for flexible iOS screen dimensions since Day One (2012). It was a habit I already had, from MacOS development, and all my apps work in landscape mode.
I am interested in seeing if I can leverage running on inside and outside screens. That might be interesting (but I don’t know if that’s possible. They may switch off the outer screen, when the device is open).
I’ll bet that Apple may ship an Apple Pen Mini, for these.