To be honest, I think NotATether is right. As far as I know, there are no 'reserves' of ASICs ready to turn on as soon as the Bitcoin price skyrockets. They may relocate if it gets too expensive to mine somewhere (either by moving own operations or selling the devices and closing a facility), but they essentially keep running at all times.
But, the profit is what motivates them. Some miners might not do anything, but the rational behavior if the price skyrocketed (ceteris paribus) is to acquire more ASICs. As the marginal cost becomes lower than the price, you should acquire the machinery until there's the equilibrium point between price and marginal cost.
There are no more miners to acquire, though. Manufacturing of these chips is the bottleneck right now, as far as I know.
This is generalized. Other factors might affect their behavior (such as price of energy, price of ASICs, state intervention etc.), but the bigger the price fluctuation, the less the importance of these factors. I'm pretty sure that if we fell to $1,000 per BTC, some miners would shut their business down, no doubt.
I believe they would shut down their business, sell the miners to people who have access to free electricity and the machines would keep running.