if halo wars doesn't outsell kz2 consider halo wars a failure.
halo3 (which is the same fanbase halo wars is marketed towards) sold 9M. the absolute best selling ps3 game is GTA at 5.4 M.
I think the best kz2 can hope for is around 4M and the anything under 4M would be huge disappointment for a game with the word "halo" in it.