I think, a framework which wants to support the development of innovative user interfaces nowadays must at least offer good foundations for each of the following:

• stable (persistent) and personal (=user-centered) geometries,
• highly individualizable item/entity rendering,
• out-of-the-box user-input validation techniques,
• offer a declarative way for the creation of arbitrary and complex user-dialogs.

A plus would be:

• utilities for working with 2D/2.5D space,
• allowing constraint-based development,
• offering a scene-graph like rendering engine,
• a neat and simple way to deal with i/o.

As well dealing with a pretty and stable API as with having a reluctant dependency/library management, saves work (and therefore lifetime).

I would consider any framework which supports this set of functionality already very helpful. Anything dealing with i/o, semantic networks and occurences is still another topic and this is, if everything would be just about developing new user-interfaces.

About developing software platforms in generell, I will keep it with (1) the Google+ rant of Engineer X on doing what your best at (in this case, help other people/developers to develop) and (2) doing that right as well as find some very good answers on why you need to start building this at all.