as I pointed out on page one of this thread - there just isn't enough time to ship it in september. The only developers who have it are the ones at WWDC, which Steve said represented only 1% of all developers. Does anyone really think they can release a major upgrade to the OS in Sept that they haven't even seeded to all developers in mid July? In order to release in Sept, they have to go GM 2-3 weeks before that so they ahve something to ship. Does that even leave a month to get multiple builds into developers hands and to the required testing and bug fixes?
What will likely happen in Sept is the ship date will be announced. Apple will then do plenty of promotion to hype that ship date.