Why not? With Natal coming microsft needs the money to advertise it, and besides that Gears of War isn't that big of a hardware bumper just like Halo or CoD.
I think they could very well get rid of GoW exclusivity, save some bucks and Epic makes more money on multiplatform gears of war.
"More money????"
Yeah, I bet with you that Gears4 for the next gen consoles will have a development cost so high it will take 4 or 5 years to produce.