TUAW claims that they have heard from an "anonymous Apple reseller" saying that Apple has instructed them to remove all Apple TV displays and literature by September 30th and that there would be a webcast "kick off" on September 30th.
We have not yet heard any verification of this information from any other resellers.
Update: The marketing materials licenses are simply expiring at this date, so this does not mean that Apple TV's are about to be updated.