No one can precisely predict the time of bubble burst. There are still many ppl who are buying up and ignoring the looming risk. They are attracted by the profit.
When you see a buildup like this the odds are in your favour that if you switch to a cash position hold out a few months and wait your likely to be on the winning end of the market since bubble collapses can impact valuations significantly.
If your a risk taker playing the squeeze against the Fed and measuring sentiment can be a double scoop.
That said it never hurts to wait when their is potential for a down burst as you get more shares from the weakened leverage position holders, with Greece in the Eurozone, high leverage markets in China and pushing new highs in the American exchanges the patterns seem to be indicators of some shakeup how much we will need to wait and see to determine.