Activision makes the call which developer handles the game, not IW or Treyarch.
However, the game has already been in development for a year. Someone stated only Treyarch has the manpower but how can they be doing it now if the game has been in development for a year already while also having been working on all those other projects for the past year?
I believe Infinity Ward has the manpower for 4 simultaneous SKU's (CoD: MW2 for PS3, X360, PC and Wii ) versus Treyarch doing 8 simultaneous SKU's plus collaboration on 3 others last year alone (and develop the CoD4 engine for Wii too).
IF - 90 employees.
Treyarch - 140 employees.
One must also remember that last time, IW had to develop the CoD 4 game engine. They don't have to create a new game engine this time which frees up a lot of resources.
I'm not saying it's IF for certain but they are actually the most likely studio given the circumstances.
The rEVOLution is not being televised
