While it seems pretty certain that the next iPhone will come with a fingerprint scanner, what it will look like remains an open question. A "silver ring" around the home button (see below) is the prevailing theory.
Sure, these are just renders. But they're an excellent hint at what the Eye of Sauron Siri will look like in practice. And it's likely to be just about the only difference you'll notice between the iPhone 5S and the one that came before it. More here.