It seems like folks will likely continue paying more to go to college so long as the boost in income is worth it, and colleges will continue to increase tuition until they can no longer get away with it, so it seems like that's where we could be headed.
Why it didn't happen before, I figure could be due to public schools setting a very low bar and private schools had to remain at least somewhat nearby. But as the government continues to pull funding from public higher education, it becomes more and more private, i.e. driven by the market.