Joshua Topolsky has posted a mockup of the iPhone 5 based on information from "a variety of sources."
The rumor consensus to date has been that the iPhone 5 won't be radically different from the current iPhone 4, basically just updated specs, but Topolsky says "that’s not the story we’ve been hearing at all."
In a sketch supplied to us by a source (on which the image above is based), the home button is doing double duty as a gesture area; this falls in line with testing we’ve seen for gestures on the iPad, and our sources say that gestures are definitely coming in a future version of iOS. The home button will likely be enlarged, but not scrapped altogether. Furthermore, we’re hearing that the screen on the device will occupy the entire (or near to it) front of the phone, meaning almost no bezel.
According to Topolsky, the screen will go up to 3.7-inches (while keeping the current resolution) and pixel density goes from 326 to 312ppi, which means that Apple can still tout it as having a Retina Display.
It will also be the first iPhone to ship with Qualcomm’s dual GSM / CDMA Gobi chipset making it the first true world iPhone. Although the Verizon iPhone 4 ships with a Qualcomm MDM6600 chip, it doesn't work in both modes.
Update: Josh posted another i5 mockup to the same post -- this time with design queues from the MacBook Air (instead of from the iPad 2 like above).