Comment by dcolkitt

That's a really interesting scenario. But I'd imagine if double-spends became a persistent threat, they'd just hard fork to a slightly different hashing algorithm. That would brick all the pre-existing ASICs.

In the 2018 bear market, BTC lost 82% of its market value peak-to-trough. Double spend attacks by dark ASICs didn't become a factor then. So most likely you'd have to see BTC fall by 95% or more before this became a threat.