I have a feeling that's what Firefox Hello will eventually become (if it gains traction).
As it stands, I can already post a link in this thread and anyone who visits it from any WebRTC-enabled browser (including mobile devices!) can immediately start a video chat with me[0].
That's not federated (yet), but if it catches on I see no reason why it won't be.
[0] If I weren't in the "quiet room" in my coworking space right now I'd try it as an interesting experiment in the HN community. :)
Signaling is intentionally missing from the WebRTC spec, and that is the "interesting" part here: without open and interoperable signaling, you're just preserving the status quo of proprietary video chat services such as FaceTime, Skype, Hangouts, etc. Just like HTTP enables proprietary services such as Facebook, Twitter, Google Plus, etc.