No one outside of Apple, and likely very few inside of Apple, if anyone at all at this early stage, knows what the 2012 iPhone will be called. For the sake of convenience and familiarity, we've been using iPhone 5 (or whatever Apple ends up calling it).
But Apple can call it anything they want. iPhone 4G. iPhone 4GS. iPhone 4GS Mark II Epic, LTE X. (Okay, that's very unlikely, but theit's their phone, their name.)