I strongly believe that Apple should extend FaceTime to the millions of iPad, iPod touch, iMac, and MacBook devices out there in the market (through iTunes or Safari). The current breed of iPad, iPod touch and iPhone (excluding iPhone 4) devices should be able to at least receive video from an iPhone 4 (at the other end), while all recent iMac and MacBook devices should be able to do FaceTime as completely and effortlessly as is possible between two iPhone 4 devices today (all recent Macs have an inbuilt camera). The future breed of iPad and iPod touch devices should incorporate the necessary hardware and software to allow full-fledged two-way FaceTime calls.
MacBook Air with inbuilt camera - opening the possibility of FaceTime
FaceTime could even be used as the standard way to video-chat between two Macs, or between two (future) iPads or (future) iPod touch devices (over Wi-Fi). Extending FaceTime to these additional Macintosh-based devices will ensure that millions of such devices owned by millions of people are already ready for this feature, helping to establish this feature, while ensuring that the feature-implementation is controlled by Apple in its (usual) clean/simple/unbloated and optimized ways.
Also, although FaceTime is being pitched as a way to do video-calling, I see FaceTime also being heavily used for what I call real-time opinion solicitation. When people will be doing shopping (clothes, footwear, gadgets, ornaments, etc.), they'll increasingly be calling up their colleagues/friends/relatives to solicit opinion on the thing they're thinking of buying.