My source? Common sense. Apple is most definitely not going to announce a new version of the phone that has the one feature (3G capability) everyone thinks is lacking, a mere couple of days after the iPhone's introduction in the US.

Apart from that: Jobs recently (like two days ago or so) said in an interview that 3G capability is not an option right now because the 3G chips are too big and use up too much power and that Apple would re-evaluate that option in due time. And "due time" NOT meaning next Monday.