This won't happen because:
1. iPod would need a faster processor to handle video.
2. It would need a higher definition colour screen.
3. The hard drive would be full up in a manner of minutes.
4. The iSight would drain the iPod's battery pretty quickly.
5. iPod would therefore cost a lot more.
Having said that, a low quality video attachment such as in 3G phones would be a possibilty, but I can't see Apple doing that either.