Slack, Hipchat, Campfire, etc. are all just IRC for normal people. There is without a doubt a barrier to entry to IRC that actually requires a bit of understanding of how the protocol works. "I'm in #this-channel-you-told-me-about, but no one else is in here, wtf?". "Oh, you're on the wrong network - it's EFNet, not Freenode".
There is no such barrier for the current set of chat apps. Download > Login with google, start chatting with the person who invited you. Search history? File sharing? No need to remember anything about dcc/xdcc, no need to manage servers running bots, no need to manage anything, really; it's all taken care of by the nerds that run the service.
I think one might actually be able to build a business by building a Slack that runs on top of IRC, and releasing client apps that actually significantly reduce the flexibility that a standard IRC client gives you. If you can get the on boarding flow to invite -> download -> log in -> start chatting with the people you want to chat with, you could crush slack (assuming you had the marketing budget to compete with theirs).
I think, however, that IRC will remain in some ways as a small haven from eternal September (haha, yeah, I know). The barrier to entry is a feature, not a bug.