Wall Street legend Gary Shilling warns 'tremendous speculation' is setting up stocks to tumble 30%

- Forecaster Gary Shilling warned of a heady stock market and a looming recession. - The veteran economist said the S&P 500 could sink 30% but he doesn't expect an economic catastrophe. - Shilling brushed off concerns about the dollar, saying no other currency can replace it. Renowned forecaster Gary Shilling, who predicted the US housing market's collapse in 2008, has told Business Insider that stocks could crash 30% amid "extreme speculation" in financial markets