That doesn’t mean the iPhone 5S will be released on September 10th, but just merely spoken about. You will then know when you may put the order in and buy it. Personally, I think the whole announcement and rumor mill-marketing spiel is a bit used already. The suspense is not a novel idea any longer. Where is the surprise if the same rumor, then unveiling, and then low demand that gets sold out right away happens year after year, after year.
That being said, it is a firm date on September 10th that you’ll learn all about the iPhone 5S features, specs, and everything you’d like to know about it along with purchasing one.