The name Wikidata is already taken, by the group of projects that aim to provide reusable static and dynamic facts. So for example, Wikidata will have a variable for {{population of Spain}}, that can be added to any Wikimedia project, but only needs to be updated in one location (or could be tied into an official U.N./Spanish xml feed for complete automation) http://meta.wikimedia.org/wiki/Wikidata I don't know how far along any of the experiments are, or how close we are to getting it integrated to English Wikipedia, but I'm aching for it like nothing else...
As for expandable/tangential content sections, I adore the way Encyclopedia of Life's demo looks. Click the play button at http://www.eol.org/home.html for the "novice-to-expert slider" about halfway through. I think that's the lofty target we should aim for.
Quiddity