It looks like the iPhone doesn't even need to be out yet before reports about new versions of the device start to appear. It seems that Apple has contracted Quanta Computer for an order of iPhones that will have a different design.

DigiTimes reports that Quanta Computer has received

an initial order for five million iPhones from Apple with shipments to begin in September of this year, making the company the second contract maker for the iPhone after Foxconn (Hon Hai Precision Industry), according to a May 29 Chinese-language Commercial Times report.
The iPhone produced by Foxconn is designated for the US market, and those manufactured by Quanta will be similar in function to those from Foxconn but with a different outer design to fit different markets, the paper quoted sources at Taiwan-based component makers as saying.
While at a first glance, this looks like the most unlikely iPhone rumor, it is possible that there is truth to it.

The iPhone is much like the iPod, there is little you can in terms of improving the original design. Considering the fact that the entire front of the iPhone is the screen, this only leaves the back. As such, a different outer design seems unlikely.
On the other hand, Apple will be releasing the iPhone to other regions of the world later this year and the European version is rumored to have 3G capabilities. If this is true, then Apple will need a differently designed iPhone, one that has the camera on the front to allow for video conferences.
While being slightly more than just a face lift, a front positioned camera will be made for a different outer design that will be destined to a different market than the existing ones. Also, considering that Apple said the iPhone will be hitting Europe around Christmas, the September shipping date also fits in nicely.