There is no reason to rewrite a new UI in QT unless you want to use the "cool" new library.
Native Hildon widgets are not equal to widgets that Qt provides. I you want a uniform look and feel all over the UI, you need common building blocks. Of course this can be accomplished e.g. with GTK and Qt, but it's much simpler with one UI library. Especially when the platform and UI evolves constantly.
Nokia really are hopeless at drumming up interest in their future products - what was to be gained from taking down this video? Unless it's completely unrepresentative of what is coming of course (which may not be a good thing either).
