GMO Funds forecast a real, annualized return over the next seven years (the period that they consider to be the most predictable) for US large cap stocks of -5.7% to -2.7% (depending on interest rates).

gmo.com: Investment and Asset Management | Americas

Whatever the best forecast is, it's not likely to be high, or even average.

Furthermore, corrections are usually sharpest in the first year or two, so whether the real, 7-year return is -5.7% (GMO) or the nominal, 12-year return is -6% (Hussman), the 1-year or 2-year or 3-year return can be expected to be lower than the 7-year or 12-year annualized return. My wild guess would be that we will see a significant correction (say, 30% or more) within the next one to three years for the S&P, and an annualized return over the next 7-12 years for the S&P that is lower than T-Bills.

rrr12345