Well I read somewhere it's going to be called Xbox Blue. Cause they're trashing HD DVD and picking up a Blue Ray player for it. Which means it won't be Backwards compatible but that might just be rumor
I don't think there will be a new Xbox anytime soon. I mean they just updated the dashboard and can do all sorts of other updates. Why would they make a new one when they can just add updates via the internet.
And if they did make it it would have to be totally revised. Also I would name it the Xbox Revolution, Xbox Ceder, Xbox Uber, Xbox NextGen, or something like that, haha.