It really depends on what kind of advertising Microsoft does. If they put as much into the advertising as Halo 3, I can see the game selling 4.5-6 million first week. Mediocre add blitz and you still come up with 4-4.5 million first week.
Overall I say lifetime it will do 13-15.5million (this is if the game is actually as good as it looks).
"If you've got them by the balls their hearts and minds will follow."
Quote by- The Imortal John Wayne, the original BADASS!