The all newly redesigned iPhone 5S is slated to be announced on September 10th. According to BGR, this version of the iPhone is going to be largely different than the iPhone 5 with a lot of upgrades. The news originally stemmed from an AllThingsD article and source that has in the past correctly identified launch dates.
The iPhone 5S will have expanded hardware capabilities including a faster processor and a redesigned external theme. The phone is also rumored to have an upgraded camera, and possible fingerprint scanner. It is unclear at this point if Apple will joint launch a new iPad and iPhone 5C which supposedly will be a low cost alternative to the regular iPhone.