I don't see why your focal point is on the productivity of miners.
It doesn't matter how many miners are mining, as long as there are still miners. BTC are being generated at the same rate no matter what.
BTCs may generate at the same rate but, as it takes more and more to generate them it is not worth it to mine. Miners cashing out is the problem. The more miners decide, I'm done, the more pressure on BTC.
So prices are temporarily depressed as miners cash out? No big deal. Who cares. Buy them while they're cheap.
And also, I think a lot of miners may quit mining, but keep the bitcoins for a better future price. Just because they stop mining doesn't mean that they will cash out.
Take me, for example. I've mined and bought. If things don't improve price wise, but the difficulty keeps going up, it'll probably be about a month, maybe two before I stop mining because it is too much trouble for the price. But there is no way I'm selling my hard earned bitcoins. I'm holding those for the long, long ride.