According to iPhoneItalia they have a “very reliable source” who claims that Apple will be launching the iPhone 5 on October 5th on Swisscom’s network. The source is a senior executive at Swisscom. The story says that the October 5th date is the “rest of the world” date. In other words one month after the US release date: September 5th.
Apple would inform wireless carriers of their iPhone 5 intentions ahead of time, so there may be something here, but for now it is just a rumor that is unconfirmed.