Basically Infinity Ward got sick with the Call of Duty franchise (I would be too. :/) and wanted to make something else. They either quit or got fired but they're working with another company which I can't remember. I also heard rumors they're working with Bungie?
If MW3 really is coming out then TreyArch is doing it.
Talk about fast, holy stuff these bastards are money whores. Knowing me though on how much I hate this stupid mainstream gaming I'll probably wind up buying it anyways.
Bungie actually denied that they were working together.
I probably won't be interested in it at first, and I won't play any multiplayer at all, simply because I don't like the games online, and the community is terrible anyway.
But, I will most likely find myself playing the campaign, like all over CoD games.