why dont you compare it to some Wii FPS games and see where it will land. Like CODWaW and Red Steel. Both of those games sold well over a million, and if The Conduit sells a million I think HVS and Sega will be pleased.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut