Definitely not 15, maybe 10, but I'd honestly expect more around 8 million or so. The install base just isn't there and most games sell their majority soon after release because later on the hype is gone and new "hyped" games occupy everyone's $$$.
A bundle would help that figure.
PSN ID: Sorrow880
Gamertag: Sorrow80
Wii #: 8132 1076 3416 7450