It's likely MS will try to add new franchises with the new gen. It's rumoured already that they have Rare working on a FPS game and something else (cannot remember where I heard it though). MS are sitting on a wealth on franchises they are doing nothing with at the moment. They recently renewed the rights to Killer Instinct but I doubt they'll do much with it. They have Rares back catalogue of games including Conker, Viva Piņata and Perfect Dark (which we haven't seen since the 360 launch). Not sure if they still own the rights to PGR but obviously Bizarre Creations is no more so someone else will have to take it over.|
Also not mentioning many of their Original Xbox games they never renewed. They have a rich library of games to pick from. But more likely they will try to create something new for the next generation.
The only thing they do lack is quality 1st party development. I question Rares ability to create anything resembling their past games. Lionhead are a shadow of their former self. Bungie are no more for MS anyway and again Turn 10 seem to be slipping with each release or coasting). They have a wealth of creative franchises but I just do t see who's going to make them for them. I expect a dramatic dip in quality for the Next Xbox launch year, only being filled by 3rd party developers.