I know that previous articles have been written about iPhone video chat, however, most of these articles were written prior to the release of the iPhone 3GS.
BoyGeniusReport.com has some awesome images that show (possibly leaked) photos of what iPhone video chat could look like.
I do know that from reading feedback from users on the web, iPhone video chat is a feature that is much anticipated and desired from iPhone users.
And since there are a whole lot of video chat / mobile phone integrations on the market, I see this as another move for the iPhone to become a dominant player in the mobile phone market.
Here are some possibly leaked photos from BoyGeniusReport.com: