These theories sound vaguely plausible.
I would rate them as about 5% true and 95% false, as explanation of the past and prediction of the future.
The satisfaction of learning to do something difficult isn't going away, and the social status associated with it won't either.
Sure, I guess. But today, something like 30% of people play music or sing regularly enough to say they do it (ie, not very much at all). Even a couple of generations ago, it was much higher. It's not going to die out, but I think a lot of people are asking themselves if they want to bother.