as for video chat, AT&T doesn't have this supported on any other video-capable phones, some European networks have it...so i don't konw if they'll do that...
Exactly, here in Spain we have been able to video-call for a long time, and it's a beautiful feature save for the cost, which is a lot higher than a audio-only call. Another obstacle for wider use of video-calling is that you need a mobile phone with power to handle it and a front facing camera, which very little people care to get.
.. but my other mobile phone (Nokia N70) can handle videocalling very well with an ARM9 200Mhz, and 32MB RAM so I think the new iPhone would be more than capable of delivering videocalling and iChat like videoconference (h.264 of course) through WiFi