Actually an interesting idea - in this context Facebook's purchase of Face.com might seem prescient.
Separately - as data gets cheaper and video chat is further optimized, video chat over 3G/4G becomes more feasible. Probably our answer to this is in the countries that have abundant bandwidth? What do high schoolers in Korea/Scandinavia use for video chat?
Adaptive lossy compression already does that implicitly. Static background content will consume very little bandwidth. A bad case might be if you are riding in a vehicle so the background is moving a lot...then it could be good to eliminate it. But this use case doesn't seem so common today.
Potentially, but I think the gap facetime/skype fills is real time, whereas snapchat is async no matter how you slice it. It's explicitly a call+response method of communication that the receiver can engage right away, or view tomorrow, and respond tomorrow. While sending a recorded video or highly compressed pic will benefit from more efficient data transfer, its still not quite the same as a live open video chat.