Reasonable...I would expect the sales to taper off after December though. So there is a likely hood that the actual number will be less than your prediction.
I dunno, my thoughts on this are that Sony has already pulled their trump card, the slim. They have nothing but price-cuts and games to carry them for the rest of this gen, and with MS getting Reach and a pretty hyped up motion tracking system, I think Sony will lose much of it's current momentum to that.








