Definately possible. The MGC user tracking for Mass Effect is pretty freaking huge. It's right behind Call of Duty 4 and Halo 3, but ahead of Assassain's Creed.
But like everything else, time will tell. ioi can't go off "ideas" on software sales. However, if the X360 did = Wii/PS3 software (which would probably be around 3m units), we should see Rockband, Call of Duty 4, and Mass Effect a bit higher.
Totally random o/t: I went to Best Buy today and saw 2 guys (mid 20s) buy a X360 Elite and Rockband. I about died. It was $600+
Back from the dead, I'm afraid.