I would also hope for such incremental change, but I don't see it happening. If you take a look at historical development of desktop OS UIs, you'll see all concepts established in 80s and not much (any) progress since then. Icons, buttons, menues, windows, even whole applications (file manager) are unchanged, while there's very few new UI elements (date picker, for example).
VR should be considered as completely new medium. 2D windows in VR should only be used as backwards-compatibility layer. Re-inventing every part of interface at the same time sounds great to me. Let's make as many competing solutions and then pick ones that work the best. This paves the way not only for rich VR experience, but also for AR.
