A trusted source has told BGR that that AT&T plan to release the iPhone 5 during the 3rd or 4th week of September. They have cleared the schedule of employees to ensure that there will be all hands on deck through to October. Presumably so they are able to deal with the onslaught of those wanting to get their hands on the iPhone 5.
BGR: AT&T iPhone 5 set for late September release
Another source at AT&T has confirmed that there will be a huge training event for all regional employees and this has been set for the first week of October so as not to compete with a big announcement that Apple will be making. This of course would be to introduce the latest generation iPhone, the iPhone 5, and possibly other iOS device at the same time. The press conference is set for 12th September and it is thought that they could announce the launch of an iPad Mini at this time too.
Rumour has it that the iPhone 5 will feature a larger display than any of the iPhones we have seen so far. If so it would be longer and it has been rumoured to have a ratio change which would be better for watching movies in landscape orientation. It has also been suggested that the dock connection will be new and this would mean that all accessories designed for current iPhones would be incompatible.