Well one of the main reasons IRC hasn't developed much is because it's just as useful now as it was 10 years ago. The only real issues with IRC as a text chat protocol are that it was designed for 8-bit text encodings whereas if it were designed today it would almost certainly be built around UTF-8 to eliminate the annoying encoding problems.
Everything you're talking about is covered by DCC, so there's no reason for IRC to be changed. DCC is already a peer-to-peer (Direct Client-to-Client) protocol. Video and voice chat are already possible over DCC, and although I probably wouldn't use it much I think mIRC could benefit from supporting it so I agree with you there.
