Nothing any of us do today will exist in 500 years, but I suspect Beethoven's Ninth will continue to inspire.
For comparison, the 500th anniversary of Jean d'Okeghem's death was commemorated in 1997, and there is small but significant scholarly and performance community active today which are devoted to his works. Although there is no unbroken tradition of performance for Okeghem's music, we would like to think that we are his heirs in some way. There was a particular touching anecdote relayed by Fabrice Fitch that on the very evening of the Okeghem anniversary after the conference, he gathered with a few fellow musicologists, and, using a photocopier as a lectern, sang the 16th century lament "Ergone conticuit" written in remembrance of Okeghem.
Similarly, the 500th anniversary of Josquin des Prez, a much bigger star, was celebrated last year via numerous CD releases, journal papers, and concerts. Josquin is so famous that even though he may have been neglected for 100-200 years he may well be considered part of the enlarged classical canon today. In fact Robert Levin in a lecture explicitly mentioned Josquin when he asked the very same question about Beethoven. Going by these examples, it seems likely that Beethoven will endure.