Classical music will last forever. It may not be performed by symphonys in the future but the music will survive. It’s indie, rap, disco and other disposable music that will be easily forgotten.
It will survive and it will flourish. There is a move amongst the current generation of composers back to tonality. Beethoven and Copeland will be performed widely in concert halls alongside of people we have not yet heard of a hundred years from now, just as Sophocles and Shakespeare will continue to share the stage with who knows.
Music and the directions on how to perform it exist in so many mediums that it will always be prevalent so land as mankind dwells on Earth or in the stars. Humans are curious and attracted to beauty and look to the past for guidance and inspiration.