Look at what's being taught in high schools today. A subset of those will be considered classics a hundred years from now. (Seriously. A classic is something that has had broad exposure in society and enough literary value to be taught.)

That is a much harder call. Traditionally, the classics have been the books worth publishing. Since it was expensive to print books, relatively few books were worth publishing. Thanks to digitization, that is changing. You can now go to Project Gutenberg or the Internet Archive (or MobileRead) and find a deluge of digitized texts. It is entirely possible that hard to find texts of the past will be rediscovered and usurp the traditional classics. (The interest in historic books won't change, though tastes in those books may change.)