The volatility tends to turn earlier than tops.
In 2007, the volatility found its overall bottom (when looking at the sedond contract) in feb07, 5/7 months before the last tops.
In 2015, we are on new successive marginal tops and the bottom of vol was reached 7 months ago in Jun14.
From here whatever happens the the 2month forward vol will be well bid because even if SP500 was to increase the market would purchase more options to protect its downside not allowing vol to mark new lows.