9to5Mac dug up references to video conferencing—hosted on Apple's own servers—as well as group chat rooms and chat moderators in iPhone OS 4. That's good news.
The group chat and moderator stuff are unique to iPhone and aren't found in iChat on the Mac, so it's more-or-less legit as far as it being FOR the iPhone. 9to5Mac guesses that the group chat is for the Game Center, which makes sense, since if you wanted to have a group chat now you can do so over the regular phone network.
The video chat is definitely something we're looking forward to though, and hope that it's interoperable with iChat on the Mac (maybe an iChat for PC too). But to be fair, the existence of the code inside iPhone OS 4—especially right now—doesn't guarantee that the feature will come at OS 4's release in Summer. [9to5Mac - Thanks maj0!]