If Libera.chat gets 60% of the users, freenode would still be the second largest IRC network. I think there will be a enough inertia among people/projects who don't follow hacker news or internet trends for the remainder of freenode to retain an audience.

The bigger question is if they retain enough server sponsors, who may be paying more attention. They might defect to libera.chat or OFTC, or just decide the whole business is not worth their while.