According to reports, the iPhone 5S is set to begin trial runs of iPhone 5S production. Of course this is all rumor and speculation, and these sorts of things always come from obscure sources.
Furthermore, these rumors come from Commercial Times and Digitimes. That just about says it right there. Digitimes is probably right less than half the time. While that can partly be because some of the products they report on never make it past the testing stage, it still tarnishes their reputation as a credible source of Apple information.
That said, the iPhone 5S is pretty much a given, just like an iPad mini with a Retina display. Unless Apple changes up their naming convention, or does something totally unexpected, we’ll probably see an iPhone 5S in roughly a year’s time.