Many people enjoy Monteverdi, Tallis, Bach, Guerrero, Josquin, Handel, Lully and other composers of 200-400 years ago. They will continue to do so 200-400 years from now.
Some of our modern composers are being added to that pantheon, and more will be added as time goes on. Even some of the popular music will survive.
Some composers will fall out of favor, but it is there to be rediscovered.
Folk is always a reservoir of ideas; it will not disappear.