Are you sure it hasn't been Sept 10th all along? Someone in one of the boardgamegeek forums indicated that Wizards ships to FLGSs first and delays the shipment to mass market stores a bit.
This makes sense both from a strategy point of view (i.e. supporting the FLGS that promote the hobby) and from a logistics point of view (i.e. there are only so many boxes on the first boat, so someone has to be first).
Copies of Ravenloft are in FLGSs now. People who want to pay the extra 10-20 bucks to have it first can go pick it up. Personally, I can wait a couple of weeks to save a few bucks.