Just like the new iPad, the next-generation iPhone probably won’t have the number “5” attached to the end, and it’s not for the reasons that you may think. Let’s just say that if they did keep the numbering scheme, things would get awful strange 7-10 generations down the line. Continue reading for more information.
The original, 2G iPhone was just called The iPhone. The second iPhone was the iPhone 3G. The third iPhone was the iPhone 3GS. The fourth iPhone was the iPhone 4, which made sense from a marketing perspective because we were all used to the “3” from 3GS in the predecessor. And it was literally the fourth iPhone. The fifth iPhone is the current model, the iPhone 4S – you’re already using an iPhone 5.
[Source]
