Assuming that Apple will follow it’s usual release schedule that it’s kept close to over the past 5 years, this is what we can expect after the September 12th Special media Event.
2-3 days after the event, probably Friday September 15th, at 12:00 AM PT, we can likely expect pre-orders to begin.
9-15 days after, but most likely 10 days after on Friday September 22nd, we can expect the official launch of the iPhones announced.
As this is the 10th anniversary iPhone, and because you can never really accurately predict what Apple will do, there could be deviations from this – there could be no pre-orders like when they released the iPhone 5S, or, it could be a day or two different on the dates. Rumors are flying that there will be very short supply on the iPhone 8, so it could actually have a later launch date than the other 2 iPhone updates said to be offered this year.
We’ll find out all come Tuesday, September 12th. The event is at 10:00 a.m. PT at the Apple Park campus. An iPhone 7s, 7s Plus, LTE Apple Watch, 4K Apple TV and the much speculated about iPhone 8 will all likely be announced.