dude,
you'll find if you have a look at the currently support applications for the IPv6 platform, such unix clients like ircII, BitchX, epic and irssi currently have IPv6 support, and it is likely that developers will be working on a next generation IRC protocol. dont make assumptions of such nature until you actually have read into the documentation on it. may i suggest the Linux-IPv6-HOWTO for a starting point?
have fun...
goth1c