Well, that's assuming Rare finishes Perfect Dark Zero for the Xbox 360.

Haha, I still remember the post of Microsoft expecting Rare to make 5 Xbox games in 2 years. So far the only game made was Grabbed by Ghoulies. With the only other games coming up being Conker, and Kameo.
They've made 4 GBA games though (not including DKC 1 & 2 because they're only ports). It's very RARE to see them not with Nintendo in some way. What pun?
Well anyways, (I highly doubt this is the secret game btw), maybe this is a game made by Rare. Probably not, because we'd see it on DS2.