Nothing to do with Infinity Ward simple fact that microsoft have paid for the privelege in some way, same as they did with GTAIV. I guess they will charge £8 a pop but of that an extra £1 will go to IW if they can have it a month early. It means they can say "get all the big exclusives first on Xbox, don't bother with PS3 cos you'll have to wait". If I was a first time buyer it would make me think.
Guess sony aren't prepared to pay or don't think that they'll need to, they think the fan base is too sticky to care.
I'm not that fussed, it's just business. Would rather have them now but it's not much money really so I don't mind paying. You'll all get them inthe end.