Scenario 1:
If the iPhone 5 is due out in the fall, why are parts such as the home button and sim card tray circulating so early? No way would China have their hands on production ready parts a little under half a year before it's even announced. This is fake.
Scenario 2:
The iPhone 5 is due out at WWDC given the recent plethora of part leaks, but it may not be as radical of a redesign as we initially though. Furthermore, just because this is a flat sim tray, doesn't mean that it's not a bigger screen or thinner, ect.
The metal frame of the 4S with the improved antennas was leaked before the Verizon iPhone 4 was released. Back then it was thought it was an early design, but later one it was proved to be from the iPhone 4S. That was in January or February if I recall correctly.