Great chart by Research Affliates:

This really puts the “stocks for the long run” numbers in perspective. Yes, over the past century, u.s. stocks have returned about 7.2%. But based on today's valuations, we're looking at returns of 0.5% to 1.5% per year, depending on which metric you use.

Does that mean a crash is coming tomorrow?

No. But it does suggest that a little caution is warranted. And to the extent possible, it makes sense to diversify into market neutral alternatives.