On Slashdot today...
http://developers.slashdot.org/article.pl?sid=04/06/15/2250215
What this means is that, while development continues on the Ogg Theora video format, any video encoded with the existing encoder will be playable into the future.
I think we are now in a position to go ahead and start adding Theora videos to Wikipedia, if anybody has suitable video to add!
Given this, also, http://meta.wikipedia.org/wiki/Video_policy becomes a much more relevant discussion.