Android seems to be making the leap acceptably. And, who's to say that there aren't going to be slight variations between the different UI's (Apple's 10" tablet is rumored to run a THIRD version of OS X, a hybrid between desktop OSX and iPhone OSX), each one optimized to the specific hardware in question.

Which is just my way of saying: I'm not convinced by your pessimism about them being able to run Maemo on a range of devices spanning 3.5" screens up to 10" screens. And, frankly, even if it is just a 7"-9" giant maemo display, I'd probably be happier with it than I was with Ubuntu-UMPC on a 7" display, due to the superior and consistent UI integration I've experience on Maemo over Ubuntu (and I _like_ Ubuntu).