These forums are not an authoritative source of anything -- in fact, this very statement is not authoritative regarding its very subject. 😉
In all seriousness, some folks believe the iPhone naming convention has everything to do with its generation. Of the five generations of iPhones, only one of them has been named precisely after its generation -- iPhone 4. Even the first iPhone was simply called iPhone, not iPhone One.
The naming convention seems to have more to do with distinguishing the overall design of the device:
iPhone
iPhone 3G = new radio, new design, new name
iPhone 3GS = faster guts, same design, just append an S
iPhone 4 = new everything, new name -- and happens to be 4th generation
iPhone 4S = faster guts, (mostly) same design, just append an S
iPhone 5 = new everything, new name -- but 6th generation
Doesn't make much sense to call it anything other than iPhone 5 unless one is in the name must match the generation camp.