The leak that asserts iPhone will have a new model early next year that will download Internet content significantly faster over AT&T than the current model's often s-l-o-w performance over AT&T's EDGE network.
I'd expect an announcement of the faster iPhone in early January, either at Macworld, or at the Consumer Electronics Show. But I don't think this changes things much.
First of all, you can expect the next-gen iPhone to cost more. I'd bet $499. But since Apple has seen a propensity for dropping iPhone prices only a few months after release, any consumer with a lick o' sense will wait this one out.
Second, I think that most people who really wanted an iPhone already have one. They've paid between $399-$599 in recent months. Only the obsessive-compulsive, or the fanboys (who are already largely obsessive-compulsive) would buy another iPhone. And I can tell you there ain't gonna be any exchange.
Third, near as I can tell, the EDGE-as-slow-as molasses has never been a make-or-break decision arbiter for prospective iPhone purchasers. Oh sure, there have been some complaints, but I don't detect slow Internet downloads as being a barrier to purchase for the more than one million iPhone users so far.