Here's my take. The Shiller PE points toward stocks being quite expensive. As such, if you get into the market now it is unlikely for stocks to produce an above average return over the next 10 years. Or, 10 years from now the intrinsic value of the stock market is not likely to be triple or quadruple the current value - even if we have consistently very strong economic indicators. Sure, the market can move higher for a time. The probability of the market moving higher for a given duration decreases as the duration increases. It is highly unlikely that the market will produce above average returns, year after year, for the next 7 to ten years. The only way to get an above average return over the next 10 years will be to buy after a correction.
I think it is impossible to predict when a correction will occur. But, I would be extremely surprised if a correction does not happen in the next year or so. The likelihood of a correction not happening in the next year is slightly less than, say, Richard Dawkins becoming a Southern Baptist.