A new rumor suggests that the iPhone 5 will have an aluminum back to replace the iPhone 4’s glass back. Along with the new chassis, there will also be a redesigned antenna that does away with the external design in the iPhone 4. You might remember that this issue led to Antennagate.
The new antenna will put the iPhone’s antennas back into the Apple logo, similar to the way the Wi-Fi iPad housed its antennas. There was even a patent that turned up recently that suggested Apple was working with Apple logo antennas for the iPhone, so this makes sense. I guess we will find out soon enough.