The latest beta of iOS 4 has a new feature: FaceTime through email address. This could be used to FaceTime with iPads and iPod Touches, which don’t have a phone number. This could also be used when a person has wifi, but no cell service.
Another thing that hasn’t been considered: FaceTime on the Mac. Apple based iOS on Mac OS, so it wouldn’t be surprising if they could make FaceTime for the Mac, or possibly even the PC. Seeing as Apple made FaceTime an open standard, and it really hasn’t been implemented yet, Apple could use it themselves.
If Apple put FaceTime on the Mac, it would dramatically increase the number of people using FaceTime, making the iPhone even more attractive to potential buyers. It would be a smart move by Apple. Let’s see if they do it.