IRC is great. Need help with an advanced math problem (or a basic one)? Try #math on freenode. Need help with an esoteric Python problem (or a basic one)? Try #python on freenode. Need help with ${anything_else}? Try #${anything_else} on freenode. Etc. (If there isn't a freenode channel for your topic, then Googling for "topic IRC channel" will usually turn up something on some other IRC network.)

I can't think of any other tool which solves the same problem as IRC, so it seems doubtful that IRC will be joining the ranks of the dearly departed anytime soon.