Modern Warfare 3 hasn’t been officially confirmed by Activison yet, but if these reports are correct we could be looking at a release in November; judging from previous release dates in the franchise.
Infinity Ward aren’t out, they’ll be working closely with Sledgehammer as the two studios are equally sharing duties on the production of the single-player aspect of the game. Raven Software are said to be working on the multiplayer portion.
We’ll try and get this confirmed with Activision shortly.