Just saw this post on The Escapist (article) . The Piece says that at least two of the main characters of the Metal Gear Solid series are uncertain of their participation Rising. Voice actors David Hayter and Quinton Flynn have not been contacted by Kojima Productions.
This makes me wonder if the game will be pushed even farther for release. if that were the case the MGS fans will be pissed since the game has already pushed... once? In any case Flynn says he would be angry if they don't use him as the voice for the main character.