People close to the details have reported that Apple will be holding a media event on October 4th. This event will cover the announcement of the next iPhone being either the iPhone 5 or 4s.
The sources also indicated that Apple plans to make the new iPhone available weeks after the announcement, so we still might see the iPhone 5 in October.
This announcement will be the first time CEO Tim Cook will take the stage instead of Steve Jobs to make a product announcement as big as the iPhone itself. It is not clear if he will be joined on stage by Steve Jobs, his presence will likely be determined by his health at the time of the announcement. Stay tuned for more information on the iPhone 5 release.