Apple is alleged to unveil the next-generation iPhone 5S and iPhone 5C in an event on September 10th. In an email sent by Nuance to its developers, it is mentioned that September 10th will be the day iOS 7 also becomes publicly available.
A developer named Owen Williams received an email today from Nuance, the makers of Siri, indicating that iOS 7 will be made available to the public on September 10th. In the email, it is written that, “As you are probably aware, iOS 7 GA (General Availability) will be released on September 10th”.
While Nuance enjoys a close relationship with Apple, it is highly unlikely that it would get information as to when iOS 7 would be generally available to the masses. It is entirely plausible that Nuance is mistakenly referring to the iOS 7 Gold Master build, which is the final build that is seeded to developers, usually seeded on the day of a device announcement. iOS 7 is at beta 7 currently, so it should not be long before it gets to the Gold Master stage, and then subsequently General Availability.
Apple is going to announce the iPhone 5S and iPhone 5C on September 10th, so we just have to wait and see if it decides to make iOS 7 public on the same day.