This game is going to stay with Microsoft because they are going to pay out their asses for it. Sony isn't going to pay much money for it because they already have enough AAA shooters to try and spread out.
On top of that, people thinking the next Xbox be out by 2010 aren't looking at how development is going these days. The hardware really is too advanced for developers make stuff out of these days. The PS3 is going to be selling for awhile to come, and there really isn't a reason to upgrade for at least another 5 years. What is an upgrade going to do? 1080p and FPS only matter so much, and these bigger projects take bigger teams which the current development process really can't handle.
At this rate the next console game is going to take 3-4 years minimum and cost millions of dollars. They will also have to learn the new hardware and somehow still make money off of their games. Its not going to happen in the next 2 years IMO.
Gears is going to be the center of the 360 lineup for 2 more years minimum before the next console is released. They don't have any other choice at this point.
