Im thinking this pic may show only PART of the new iPhone, minus some additional front-plate parts that will add (a little) thickness.
Two previous photos (below) clearly show what looks like a raised plastic lip/edge around the front (similar to but smaller than the lip around the front and back glass on the 4 and 4S). The black photo could just be the front plate put on wrong, but the white image shows the interior, and that lip looks real to me.
(The third image is just a render, but it does depict the lip Im talking about.)
If that detail is real, it adds thickness not shown in this new photo. I think this new photo is just the metal band and back, not a complete shell with properly-installed front glass.
I dont like the lip, especially since it would only be on the front and not the new unibody back (asymmetry). Id prefer the phone to be ONLY as thick as the metal band. But Im not getting my hopes up. At least the protruding plastic edge looks smaller than on the 4/4S, and the total thickness is still less.