No need to speculate, look at the price and hash rate charts in 2017. The more recent hashrate drop was even bigger. Still no successful attacks.
There's a disincentive for people with mining power to attack the network (assuming they even have enough). It makes their hardware worth less so I can't imagine anyone doing it for kicks.
Agree though that something similar to what you're saying is what Bitcoin hitting $0 would look like. Certainly not impossible but I think it's extremely difficult attack. Even more so now than in 2017.
