The game has been officially name Metal Gear Solid 4: Guns of the Patriots and will release on the PlayStation 3.
You may have heard that Snake has turned into an old, old man and it is definitely true. The trailer shows him wheezing and at one poing he collapses. Time may have gotten to him, but Otacon is returning with his same youthful appearance.
Hideo Kojima said they are trying to create "inner qualities" in the gameplay and that this is "unseen and establishes the presence only through time and the volition of the player. This will pace the way forward to a revolutionary change that will elad us away from past concepts based on ‘realism’ as we move towards the ‘natural’".
Keep posted for more info as it is revealed about the game.