One benefit of ASICs (and any specialized mining hardware) is that they decrease the threat of this problem. The marginal revenue for an ASIC miner is far higher than the marginal cost--most of the cost is upfront. ASIC miners won't turn their hardware off even if their profit falls precipitously.
On the other hand, anybody mining with a CPU, with marginal revenue close to marginal cost, will shut off the program as soon as revenue falls. This increases susceptibility to this failure as well as other attacks, especially by a 'terrorist' who begins mining at a loss in order to force all of the other miners into negative profit so he can monopolize the network.
I disagree with you. Forget about CPU/GPU mining. Marginal revenue will be very small for ASIC miners in future due to competition. But cost of mining will be very high since Bitcoin will be very expensive. Thus even small decline of bitcoin price could incur significant losses to miners and paralyze the network. Most miners won't be able to tolerate significant decline of price. Please see again my calculations in the original post.