Fimbul: Well all I know is that for now the dev of audio/video protocol/communication is available in chrome (with flag switch I think for now, or maybe in beta) and that January's release of FF should have it too.
But for the DataChannel I believe we will have to wait longer (I'd expect around 6 months, but it's just a personal guess).
After all, once the video chat part of webRTC is stable, DataChannel would be almost complete too, the major difference being the user has the choice of the datas to send/receive whereas it's fixed streams for the video chat.