That's what I tend to think as well. Announcing updated macbooks/macbook pros that don't qualify for the back to school promo, while the promo is still going on is a bit odd.
But then again, Apple announced the iPod touch around the end of the back to school promo and just didn't include it in the promo qualifier.
With iPods I don't think there would be as much of a problem introducing them while the promo is still going on since the functionality will be relatively the same. They'll play videos just as well, play music just as well. But with computers.....ehhh I dunno. I can see a lot of people just not buying a laptop and holding out for the udpated ones. The Montevina updates, the aluminum casing, possible DDR3, non exploding graphics cards, better battery life, etc...
I had friends in college who went the first few months of classes with nothing but notebook paper and the public library computers in order to secure the latest laptop and not be one of the suckers that gets the hand-me-down shovelware.
And let's be honest, that's what the back to school promo is for. It allows them to clear out their inventory so they aren't stuck with piles of out dated computers that they're then forced to sell at a drastically lower price.