Here's what hardware it will have
Here's my educated guess based on expected chips and ATT capabilities:
3G HSDPA with 7.2Mb/s download but slower upload speed. WCDMA for countries outside USA.
Better camera, up to 5MP. Probably depends on how good a teeny camera they can find. No flash. Video recording. Second camera likely, facing user, 320x240 max. Does video calls. Does video iChat. Based on an Apple patent thus far unused a second possibility is that the single camera is on a swivel so it can face either way. I think this would be less elegant looking and sturdy and so predict second camera. Support for AT&T Videoshare.
Bluetooth 2.0 using Infineon 8753. Extended data rate to 3Mb/s. Stereo Bluetooth.
GPS based on Infineon 2520. Accurate to 5 meters. Enhanced 911 support.
The CPU supports infrared but I believe that is used in the head proximity sensor so I don't predict IR remote. It supports a USB port but I don't expect that.
I'm guessing no additional charges for using AT&T 3G in the USA. I'm also guessing a May release so it is in the geek developers actual hands for WWDC and the WWDC can have sessions on the new abilities. At the very latest, they'll be announcing at the WWDC itself.