I actually think you are wrong, Adrien, and that quite a lot of the olde songs will come through.

My son is 15 and knows a lot of the music that I listened to because it's been played round the house for years and he plays in a band with me so knows a lot of old stuff. He has a friend of a similar age who writes music and plays and sings who we saw when we went to her dad's 50th birthday. When we sat and played some music later on we did several Joni Mitchell songs and the daughter knew them all along with all sorts of other stuff that would have (pleasantly) surprised you.

If it exists out there it tends to be found and reinvented and recycled. I wouldn't worry about the future it will come out ok.