I say it will be huge but not as big as Halo or Halo2. For one big reason Halo used to be the FPS king, used to. Halo was the big bad FPS nothind could even come close to, but that was last gen.
Right now Halo is not looking like all that.
Gears Bioshock URT3 CoD4 Killzone2 have stolen plenty of its hype, it will sell millions but not as much not as fast as before.
The hardcore will eat it up, but the other gamers they now have a choice Halo is no longer that one FPS you must play even if your not a FPs fan.
4 million in USA
1 million in all others.
Overall 5 million world wide. (pretty F'in good but less then the other two)
I also think GTA4 will partially responcible by stealing plenty of the Core/Casual sales, and to a much smaller extent the fence sitters got a choice of get 360 with Halo or PS3 with URT3/Haze/Socom.
