Keep in mind that the block value drop is equivalent to the block difficulty doubling. And we've already seen that happen over and over. And reverse and then recover again. I expect we'll see some volatility as people come to terms with it but we should also see the difficulty drop as some miners drop out, balanced by a price increase perhaps.
I'm beginning to miss last Xmas when mining was much easier. C'est la vie.
I would not expect the events to be equivalent. In the block value drop case, fewer BTC are entering the market which changes the supply/demand curve. If there is fiat entering the system hoping to find BTC when this event occurs I would anticipate that BTC values would rise when measured against fiat...unless the event is fully priced in by the time it happens at least.