The Call of Duty franchise is the highest selling of all time. Microsoft have always been the wiser to this and have formed strong bonds with Activision which has granted them exclusive rights to a lot of early downloadable content. Activision have even advertised the Xbox 360 as being the prefered console for the shooter.
It would be a devestating blow to Sony if Microsoft launched their next console along side one of the biggest game franchises of all time. It would then add insult to injury if Call of Duty: Ghosts was to release a timed exclusive for the next Xbox.
The idea is certainly not too far fetched, and considering Microsoft's track record with making bold moves in the industry to get ahead of their competition, I certainly wouldn't put it past them.