Next-generation iPhones likely to focus on internal improvements.
Samsung v. Apple Trial Documents Reveal Early iPhone and iPad Prototypes
Early designs include an eight-sided iPhone with diagonal corners, early Sony-inspired designs, and another model that has the same aluminum-based design as the old iPod Mini.
Of particular note are multiple iterations of the iPad featuring different types of kickstands, what appears to be a 16:9 model with wide handles on either side, and an eight-sided iPhone with diagonal corners. Also of interest is a slim, sleek iPhone prototype labeled the N90. The N90 was widely believed to be the codename for the iPhone 4, and while this narrow device definitely bear some aesthetic similarities to Apple's glass-and-metal design, this variant appears to feature a much smaller screen.
One Sony-inspired design from 2006, which bears a "JONY" logo in honor of Apple chief designer Jonathan Ive, looks strikingly similar to the iPhone 4 that debuted years later.
The Verge has a number of other images scattered across two different posts. They're worth a look.