According to Merrill Lynch strategist Richard Bernstein, since the 1930s, whenever the return from stocks has been negative over 10 years, equities rose by at least 100% over the following 10.  Via ClusterStock

There have been 30 times since the 1930s when the trailing 10-year return on stocks was negative.  The compounded average return per year after the negative decade has been 12%, higher than the long-term average of ~10%.

Of course, all these time periods were within a three year time period at the beginning of World War II.  However, given that returns are mean-reverting and that equities are cheap, I have little doubt that the next 10 years will be very good for stocks.