How about an Old Republic movie? Tell the story of the Russan Reformation, of the Great Sith War or of the First Great Galactic War!
There is so much lore and history to Star Wars, let us expand or retell that.
Arrh yes, this would be aweome. However, I don't think they will do this, since they've said that Episode 7-9 will be an "original" story, meaning that they will properly create something new. At least to start with.