The iPhone 5 will support both GSM and CDMA with the same hardware, but other than that, expect the design to largely resemble the iPhone 4 says Ming-Chi Kuo, an analyst at Concord Securities. He also says that the antenna has been improved and that the device will enter into production in August for a late September or October launch (see previous rumor). This is reportedly due to the recent Japan earthquake and tsunami, but possibly due to iOS 5 schedule as well.
Overall, the conclusion makes sense: the unibody design works very well for Apple, and they will probably tweak and optimize it for cost and efficiency for the next cycle. The company has been doing the same with their Macbook Pro laptops for some time now. Further refinements of the design will allow Apple to expand its margins, but also to continue using high-quality materials.
On the hardware side, integrating GSM and CDMA support (with a Qualcomm chip) in a single device brings the iPhone back to being a single design, which should simplify the design process and allow Apple to consolidate its engineering resources.
The real question in regards to the iPhone 5, is whether or not it will support 4G LTE networks. It would be logical that it does, but if it does not, users could get upset. 4G LTE is the most important network evolution in years, and one that has tangible and perceptible benefits to users.