Miners' margin profits have made a new low due to the recent difficulty adjustment: http://blockchain.info/charts/miners-operating-profit-margin?timespan=500days&showDataPoints=false&daysAverageString=1&show_header=true&scale=0&address=

As this continues, it will take longer and longer to pay off an ASIC and miners will be forced to liquidate a larger perecentage of the 3600 daily BTC to cover their expenses.

Miners speculatively holding Bitcoins is not the usual state of things. They are a business, and soon they will have extremely tight margins like in the past. I give it 1 or 2 more doublings of the difficulty.