The original iPhone was obviously named iPhone. No one was surprised by this. The press had already been calling it that for the better part of a decade. But one of the major criticisms of the original iPhone was its lack of 3G networking. Apple was apparently docked hard enough for this that they wanted to address the shortcoming right in the name when they released the iPhone 3G. This was technically the second iPhone, but 3G was a pretty big deal, so iPhone 2 didn’t work.
Then comes along the next iteration, technically, the third iPhone, but you can’t call it iPhone 3 when you’ve already released the iPhone 3G. The 3GS had two big differentiators, faster internals and a better camera. However, being that it wasn’t a radically new design, Apple decided it was enough to tag an S for speed on the end.
Finally come WWDC 2010, we can finally call this next thing what it is, iPhone 4. All is right in the world. Apple is set up to sequentially name their future iPhones. Everyone will be happy, and no one will be confused.
And then comes the iPhone 4S… wha-WHAT? So, now the fifth iPhone is called iPhone 4S. So, what the heck do they call the next one, iPhone 6? iPhone 5 would be incorrect. Now everything is all messed up again.
My guess is that the next iPhone will go back to the beginning and simply be called iPhone. A numberless product line has worked for both iPods and Macs for ages now, and frankly I can’t imagine what else they could do going forward.