I don't really see this happening. Too much investment for too little return, CoD would lose something like 30% of its current consumers assuming some people make the switch from PS3 to PC/360.
That said, Microsoft consider this just to try and destroy Sony. Force them to leave the hardware market by releasing hard and fast (tehe) with the next-gen console. What goes around comes around eh!
edit: But even if Sony lost all future Activision games, it might not be that damaging. Probably lose some more market share to MS. Guess we'll have to see.







