IRC3 - Is unofficial name for new generation if IRC protocol.
Why not 2 ? IMHO becouse of ircII (irc-2) client existence.
See for list of URLs of different pages with irc3 proposals and materials on this subject (also links to discussion on Advogato and W3C corresponding standarts)

I'm still thinking about implementing my own version of IRC system with ability to have modules for any protocol you like (irc,http,irc3,telnet,e-mail,SMS,IM) and internal IRC3 protocol with gates to all existing messaging systems. Also I'm thinking on implementing idea - "all is channel" (in opposit to user/channel). It was noted in RFC of IRC.