My thoughts on the 3G iPhone:
- Pretty much the same. Slightly different look. Nothing major.
- 3G and GPS
- Better camera. Possibly with flash.
- More memory
That's about it. Most of the iPhone's great stuff comes from software and the multi-touch interface. The software for both models will be the same, as Apple wants to develop OSX as a true mobile platform.
We'll see 3G (duh), and GPS (2.0 firmware includes live location tracking in maps, which is pretty poor without GPS). The better camera will be added because 3G and GPS are great, but don't complete a hardware upgrade.
More memory will be added to support more simultaneous page views in Safari as well as to accommodate games better on the platform.
I also think we'll see new contract prices announced. 3G iPhones are going to be a bit more expensive per month (maybe $5 to $10). This is due to the volume of network traffic coming from iPhone users in particular. I think AT&T will try to manage the traffic by dividing iPhone users (and hence traffic) between the 3G and EDGE networks.
And I think there will be a few more features in iPhone OS 2.0 that will be announced. We've seen new features trickle in to the developer updates, but I think quite a few more changes are planned for v2.0 final.
Oh, and we won't see video conferencing. No camera behind the screen or whatever has been floating around.