The product, having not yet been officially unveiled, does not have an official name. The casing itself says only "iPhone." The letter from Apple said "a device

The product, having not yet been officially unveiled, does not have an official name. The casing itself says only "iPhone." The letter from Apple said "a device that belongs to Apple." "G4" can be considered to stand for "generation four" and indeed this was a naming method used by Apple for iMacs and other products. Just because a lot of people think the name will be "4G" doesn't make him wrong.