"people" use skype all the time. I'm not sure video calling from mobiles will really take off. It's been available on other phones for quite a while now if you look for them. I really only want to video-call when I'm at home. For which skype works just fine.

I can't really imagine wanting to video-call anyone while I'm out or without laptop/netbook.

But only if you make it accessible to people with iPhone 4 on both sides of the conversation, and only while in range of an accessible WiFi access point?

Sure. I bet Apple has already sold more video chat capable phones in the US than any other company has in the past. The requirement of having an iPhone 4 at both ends is a barrier but at least it's easy to understand. Otherwise you've got to track down some model of phone with a front facing camera, ensure it can run the right software, install the software on both ends, and exchange usernames, IPs or whatever to establish the call. For most people, especially on family plans, buying the same model of phone is more realistic.