Well considering Halo 3 has done 10 million, Call of Duty 4 is 7/4 million (360/PS3) and those are the elite shooters it should do at least a few million LTD.
I'd say if it equals or surpasses 3.5 million (Resistance) then it would be a success. Thats not hard, thats 7.5% of their 46 million userbase.







