The difficulty suppose to adjust accordingly, but all this takes time and this would be a "real test"
for the bitcoin experiment. Basically, the (Chinese) traders and the market would kill bitcoin by setting the price below the operating costs and keeping it there for long enough to kill the network.
No mining = no transactions = game over. not only for bitcoin, game over for all cryptos.
So be careful what you wish for. You better hope $400 is the bottom.
All the mining hardware that was profitable 6 months ago still exists, it didn't vanish and the price was much lower then while electricity was the same. Current hardware is even more power efficient. In other words if a functioning network could exist then, it can exist now, even if prices drop back to previous levels.