Actually I wonder the same thing.
Tried doing some research but found nothing usefull.
The way I see it is that Activision owns both Infinity Ward and Treyarch, and just profits of of them. I mean, the name Activision has been on every box, and the CoD forums are called the "Activision Forums".
And last week, Activision's boss got a 800% raise. So they're defenitly making profit