I regret making this post
This is the 3rd thread I've responded to talking about a new game set in Orre (pun?) in the space of about 15 minuets, seems like the idea of a new game in that region is pretty popular.
I think a sequel to XD (as we already have Colloseeum 2 in the form of XD) is quite a nice idea, much better than a battle revolution sequel.
I would, however, like a prequel to Colloseeum even more though, as that would explain the back story of the region, as it has been stated that Pokemon originally inhabited the region a long time ago.