A classic almost always gains that distinction for a reason, even among children's books. A big chunk of Geisel's collected works is I'm sure destined for the same greatness and eventual cultural longevity as Peter Pan, The Wizard of Oz, and Wrinkle in Time. (Probably Where the Wild Things are will have the same fate.)

I think maybe a 1000 years from now, children and their parents will still savor them.