I think Microsoft blew their wad already for this generation.
From this point on, Sony has better 1st party exclusives coming out unless Microsoft has a lot of aces under their sleeves and that isn't really their policy. I suppose you got Alan Wake, Halo Reach, and probably Gears of War 3 but what else? Especially something with variety. Maybe Forza 3 will blow up. Maybe they can pull Bizarre away one more time to make PGR5 or in my dream world, DICE and Rallisport 3. Sony on the other hand has exclusives of better variety: Uncharted 2, Gran Turismo 5, and God of War 3, among others. Nothing too innovative but there is at least some variety there.
I imagine this is where the nine figure purchase of Rare was supposed to come into play but being as fucking worthless as they are, they're caught with their dicks in their hand.