Ooh I like that idea of a September launch rather than November.
Then they can get their launch sales out of the way, and load up stock for a separate big sales period during the holiday season a couple months later. It works as long as they've got millions of systems stockpiled by the Fall. If they aren't going to have millions of systems stockpiled then holiday launch makes more sense because you don't want a strong launch and then have nothing extra two-three months later for the holidays.
Also September launch would let them do 3D Mario at launch and then MK9 as the holiday title. Or maybe even 3D Mario at launch, MK9 in October, and then a big holiday title if they have a third big game ready in the launch window.