first, you have to order and pay for the nano you want (you get the rebate check later); they don't package the nano for you. second, the buy a mac get a nano program specifically lists which ipod models are applicable towards the rebate, and it's very unlikely the new ipods will qualify towards the rebate.
In the FAQ section for the "Back to School" promotion they specifically say that the new nanos are not part of the promotion. Also they lowered the credit to be applied to other models to $149 from $199 since the nano price was reduced.
I was thinking ther same thing but these guys have figured out all of the angles.