The iOS 9 Gold Master hasn't been released yet. I think it'll be at least another week before the public release of iOS 9.
The September event last year, when the new iPhones were announced, was September 9th; iOS 8 was released on September 17th.
Let's hope that they release the GM to developers a day or two prior to public release like last year. Considering that they made iOS 9 an open beta, the rules may have changed. Really not looking forward to updating 180+ iOS devices to iOS 9 competing for signatures with millions of others, even if they're done in bulk and parallel haha