9to5mac and iFixyouri are reporting that this could be the back for the next iPhone. Which could mean that the next iPhone would have an aluminum alloy back, and has a bigger speaker, mic and a smaller dock connector. These parts come from a Chinese supplier, who according to iFixyouri, is a reliable source.
The sides of the phone are part of the back plate, and can essentially create a box for the screen and guts to sit in. The headphone jack looks like it will be placed along the bottom of the phone.
UPDATE: MacRumors dug up the same case design in white, which was sent to them by ubreakifix.
UPDATE 2: 9to5mac has better pics of the rumored new case in black and white. They also have shots of a front panel, which has the front-facing cam aligned directly above the earpiece. Could this be real? [9to5mac]