Persistent Paper 2
Glenn Reynolds bets that books will be around for at least another ten years.
I think that's a pretty safe bet.
In fact, I'll go out on a limb and bet that "actual books" (including new books, not just archives and collections) will survive for at least another hundred years.
Update: I've changed the name of this post; I should have searched my archives before naming it. I did a post on this theme with an identical title more than two years ago, inspired by James Lileks and Neal Stephenson. Go read it.