I would definitely turn off my ASICs if the electricity costing to run them was less than the value of the BTC they were returning. I would take that electricity money I saved and buy BTC with it.
I'd end up with more BTC and the same money spent. The choice is simple.
You give miners too much credit for being rational
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Thing is, even a 65nm BFL rig is still operationally profitable at a difficulty of 4 billion and their hashrate will be statistical noise next year. A KnC rig will be profitable until ~25B and a hashfast/cointerra/bitmine/monarch, if they meet their goals, until ~50B.
OF course, all assuming todays BTC rate and depending on electricity cost, which many will value near zero in winter due to the heating.
Point being, not a lot is going to be turned off anytime soon, even if miners would suddenly start acting rationally.
I agree, we have a long way to go until todays mining rigs are unprofitable.
For me, my BFL rigs will be profitable until about 5 million, KNC until 22.5 million, and HashFast until 30 million+ (depending on what their hashrate and power usage actually is). My Avalon will be the first to be shutoff at 2.5 million (although I might try underclocking it).
"Soon" is relative, though. We will hit those difficulties early next year, and I consider 4 months from now to be "soon".
When ASIC manufacturers can sell enough machines to satisfy demand there will be nothing to stop the market to saturate to the break-even point. That will happen very quickly. The only thing that is keeping difficulty from rising faster now is the speed at which mining devices are being produced.