According to Fortune, in "Countdown to iPhone 2.0" article, Apple is gearing up for the intro of iPhone 2.0/3G.
Something is not right here...
As near as I can tell (or as far as I can tell), iPhone 2.0 is about SDK and Enterprise compatible OS X.
And if Apple were to release a 3G iPhone, they would definitely hold a big product announcement rather than let the FCC post a notice of submission for approval.
And the mid-year timing is wrong... Apple's Worldwide Developers Conference is for, uh..., developers.
In my opinion, Apple will launch iPhone 3G on January 2009 Macworld.