According to 9to5Mac, evidence in the iPhone OS 3.2 SDK (iPad only) has been found that shows possible video chat coming to the iPhone and iPad.

Also, some hidden code in the iPad telephony applications show strings of future video chatting capabilities.

Finally, 9to5Mac has found some references to iChat in the code of the iPad OS. This could mean that a front-facing camera is coming to the iPad some time soon.