It should have been done when it was first introduced: FaceTime video conferencing between iPhone/iPod Touch and desktop computers. The latest rumour is that it will be added soon. For Macs, Apple could incorporate it in iChat, while there's no mention about how they are planning to do it on Windows.
This rumour, however, comes from the French site that claimed iLife'11 was coming on August 7 with a new mystery application. Neither the mystery application nor the iLife'11 suite materialised on that date.
However, FaceTime on desktop and laptop computers is only logical. It will happen for sure. The real question is when. That's what we want to know.