I never expected the new iPods to ship or be available immediately because the back to school promo runs until Sept 7, and they won't make the new iPods part of that program. I bet they won't be available any sooner than that following Thursday or Friday.
This argument turns up a lot, but the back-to-school promos run at different times in different parts of the world. Apple is always bound to be out of luck somewhere as far as timing their releases. That doesn't mean it's necessarily incorrect this time, but if Apple really cared about it they wouldn't be able to release any products between January and September.