I'm happy someone mentioned this. I posted a thread last night about how I thought a camera signaled the end of the chrome backing. My thought process was that if a camera occupied the space the black plastic occupied, then that would mean Apple would have to switch to a back material that allowed the Wi-Fi to pass through. The only flaw in my argument, I thought, was if someone said "Well they could just put the black plastic on the other side," which I argued would not happen because it would not be aesthetically pleasing.
But apparently I was wrong. Apple found a way to retain the chrome backing even though they removed the black plastic antenna cover. I'm baffled as to how they did this. I look forward to a teardown that will show us how they did it. Maybe they somehow found a way to do it through the front of the device, like the ambient light sensor? Or maybe the signal passes through one of the several openings on the device? Those are bad theories I know, but I'm baffled as to how they did it. It's sad that they seemed to go so far out of their way to retain the chrome.