Interesting... what facts are you basing this off?
The facts that were released during and after the buy as well as the investor call on 30 October 2012 plus the fact that there has been no "coda" or anything else made public that limited Disney's rights in the franchise they bought. Disney acquired ownership of Lucasfilm including the Star Wars franchise, and all rights therefrom. This deal is public including all the details of it.
As is known, Kathleen Kennedy will be in control -- including a role as a brand manager -- while Lucas can be a creative consultant. So obviously Kennedy and Lucas could push NOT to reveal Yoda's species at all and Disney would likely be fine with that. Disney would likely be less fine with some idea that they can't use Yoda at all. Given that Kathleen Kennedy at least allowed for the possibility (and hinted a bit) that the first standalone film would be about Yoda, this also would count as evidence in its favor.
Again, the best evidence, however, are the public details of the buy out and the provisions on it. For example, for EA, Disney went with a traditional exclusive, multi-year agreement to license Star Wars to Electronic Arts. They are waiting to see how it goes. If it goes poorly, Disney could remove that license. They already canceled the game division of LucasArts, as everyone knows, but Disney went with a more traditional contract for EA for reasons that they made quite public at the time.