There's another good reason it might not get ported to the 360: motion control. Kojima has said the game will use it, and I saw a few things in the most recent video that looked like they'd be using motion control for some key gameplay actions. Maybe the controls could be adapted to work with the 360 controller, but my bet would be any motion controls would be added on top of existing control schemes (ie: I'd bet Snake rolling on the ground while prone is controlled with tilt while crawling would still be analog controlled), which could make a port of the game impossible without dumbing it down.