No music is ageless! Your reference to the classical greats presupposes that they will be as popular in 200 years as now.....but, in fact, interest in classical music in general is waning already. Music is a reflection of the society in which it exists - just as any art form. Sooner or later it passes on to become nothing more than an interesting (or not) historical footnote.
I think the only thing that will always be present in music is rhythm, the BEAT!
I think the only thing that will always be present in music is rhythm, the BEAT!