According to recent reports, the upcoming iPhone 5, which is expected to be released around June, may in fact use a very similar design to the iPhone 4. The rumor suggests that while the screen will become larger (and go edge-to-edge), the shape and form will remain the same.
The rumor comes from French Mac website MacBidouille, who has a photo of what is reported to be a case for the next-gen iPhone. Whether or not the case is actually correct, or the rumor accurate, remains to be seen, but it doesn’t seem unlikely that Apple will retain a similar form factor for their new iPhone.