Context: The Federal Reserve cut the federal funds rate to effectively nothing in December 2008, as a response to the financial crisis. It has since climbed to 1.25%, but that's still well below historic norms and not nearly enough to push yield-hungry investors out if public equities.
More from Buffett:
Waiting game: "Everybody expects interest rates to change, but they've been expecting it quite a while."
Future math: "If three years from now interest rates are 100 basis points higher, then the stocks-- stocks will still look cheap at these prices. If they're 300 or 400 basis points, they won't look cheap."
Taxes: "It'd be kinda foolish to have a gain now and pay 35% tax on it if by waiting a few months you were likely to pay 25%.