I like the second concept the best, but it's missing the volume buttons. I love how it has a removable battery, but I don't think that will happen. Also, it looks like it's made out of aluminum, which I think won't happen either. It does look sexy though!
it does have black volume buttons, really slim ones, look closely.
either way, the second mockup looks like something HTC would do,especially for the curved buttom, etc.
I'm with those saying there will never be a removable battery in the iPhone, look at the direction the Macbooks are going, iPods have always been that way, Apple is about simplicity and compactness.
For a second I thought about the chrome bezel going away, but I right away realized it's staying, take the Palm Pre for instance, the iPhone will never have a similar look. A blackberry would be more like it. I don't see the materials of the back changing anytime soon either, so I guess the design can stay the same. The Photo sensor will probably be the same so expect more MPxs, more noise as well, no flash if not a ring shaped one to take the Aluminum one's place.
I also thought about a back made of glass, that would be neat, maybe..I believe it wouldn't interfere with the reception, maybe an alloy would do, it would be more resistant to cracks from nowhere than the current plastics, less scratch-able. Who knows about being dropped, though..