15 mil in my opinion is the basement. I dont think it goes lower than that. I think 16 mil is the target and 17 if everything goes right.
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