If the supplier of my business takes Bitcoin now, almost certainly they turn it into fiat (possibly collateralized stablecoins) in order to pay their suppliers. Or maybe their supplier does. When fiat collapses, I can't keep taking Bitcoin unless my supplier does, and he can't keep taking Bitcoin unless his supplier does. And so on. So only if you have self-sufficient systems in which everyone takes Bitcoin can it continue to circulate.

Instead, most people will turn to physical barter and we will rebuild a monetary system (likely) based on precious metals.