Next-generation iPhones likely to focus on internal improvements.
Apple Starts Field Testing Next Generation iPhone (3,1)
PinchMedia who provides the analytics for the application breaks down customer usage including what specific devices are being used. This list of devices is reported to developers using internal device identification numbers assigned by Apple. In this case, "iPhone3,1" was first spotted in Pandav's usage logs in November. This "iPhone3,1" identifier does not match up with any shipping iPhones. The last iPhone released to the public was the iPhone 3GS which carries the identification string "iPhone2,1".
References to "iPhone3,1" was first discovered in the iPhone firmware files back in August, but this seems to be the first time that it has been spotted "in the wild". Apple similarly began testing the iPhone 3GS (iPhone2,1) back in October of 2008 about 8 months ahead of its launch. At the time, the usage was similarly focused in the San Francisco Bay Area where Apple is located.
There have been few details about what the next generation iPhone might include, though early rumors had pegged a multi-core processor that could enhance performance significantly. There have also been rumors of Verizon compatibility as early as mid 2010.