The radio did replace the player piano in many or most homes, so some of that substitution does take place. The compact disc replaced the vinyl record. There's no reason to believe that that growth of different channels and different media won't continue. The reason is that different media have their own efficiency of use for different purposes, and it's very rare that a technological invention is equally efficient for everything it is supposed to replace. Second, there's going to be an enormous diversity of expertise.
Libraries are at the center of trying to deal with that issue.
Well, that is nothing compared with what technology is going to bring us if the information infrastructure expands as people predict. The lack of organization has already been mentioned. We've all experienced what the information supply is like out there on the Web. There's no organization at all. That's what librarians do.