Here's a a quick concept I made for an iPhone 5. I built it with Blender and rendered it with the new Blender render engine called Cycles.
The idea wasn't to make a crazy futuristic iPhone but to make a realistic one.
There are a few few changes from the iPhone 4. The screen is larger, the body is slightly thinner but the same width and height. The front face is still glass but the back is all aluminium and takes some design direction from the Macbook Pro and recent iPad.