Yes, 1000 years from now the discs may not be terribly useful. But if there was some fantastic info on them my guess is that some creative person would be willing to build a system to read them.
But really, lets put aside 1000 years. Lets just think of 100 years, or 200. DVDs now can't be relied upon to last 100 years, but I'm confident that if someone wanted to maintain an archive of info 100 years from now they would find a way to read the discs and put them on the latest generation archival material. And this seems reasonable, we still occasionally find old films from the early 20th century and we have the equipment necessary to read, restore, and digitize the info. I suspect this trend will continue. And there are lots of people interested in maintaining huge archives of information...like google, who would love to digitize every book and other scrap of human knowledge they can get their hands on.
To me, archival isn't the question anymore. No one needs to throw obscure information into a vault to be rediscovered 100 years from now, you can digitize it and have it available forever. The real risk is what happens if Google ever goes south? It would be a shame for a disaster or a bankruptcy or something to have them just shut down and throw away their data. Seems unlikely for a bankruptcy, storage is cheap enough to justify buying almost any digitized info. But it would only take 1 extremely disruptive natural disaster, or war, or cultural revolution, etc to lose a lot of info now that it is so concentrated into a few hands.