Well Street Fighter IV is obviously an online heavy game, so I tried to compare it with another online heavy game and another fighting game. I'm using mygamercard.net for this comparison (userbase: 2.783.442):
Owners on Mygamercard Sales on VGChartz Multiplier
Left 4 Dead 502.361 1.839.652 3.66
Soul Calibur IV 295.183 1.157.847 3.92
Street Fighter IV 194.790 560.504 2.88
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So it could (could) be undertracked by ~50k. (Assumed it will sell 40k this week and a 3.5 multiplier)
Anyways the numbers aren't that off and I do think it won't have a hard time to outsell Soul Calibur IV.
EDIT: LOL I should have mentioned that I'm talking about 360 sales 
