Which means that some miners will shut down. Which means that the next difficulty adjustment will make the difficulty lower. Which means that mining will become profitable (barely) again. Rinse and repeat. The system is self-adjusting.
That is the profit per month, but you to include the mining rig cost for someone to start mining again. I doubt it will become barely profitable anytime soon.
And happens when they lower the difficulty? Isn't that directly related to the cryptographic security of the block chain?
When earlier BTC dropped enough, there were pics of huge piles of scrapped computers. Then when the price rebounded, miners had to buy the equipment all over again.