From a very popular story on TechCrunch this morning: "A trusted Verizon employee has just confirmed to TechCrunch that the carrier is having an all-staff vacation blackout from the dates of Friday, September 21 to September 30. You know what that means, right?
"The next iPhone, whether it’s called the iPhone 5 or simply the new iPhone, will almost certainly be available in stores (with lines wrapping around the back of them) starting Friday, September 21"
The story adds: "It’s largely expected that the next-gen iPhone will be announced on September 12, in usual Apple fashion. (Though the spectacle may be a bit different this time around considering that Apple’s lead presentation executive was fired in December.)"
The article gives this timeline:
"Expected announcement: Wednesday, September 12
Expected pre-order date: Wednesday, September 12
Launch date, as confirmed by our trusted source: Friday, September 21"