That’s never going to happen tho. If for no other reason that bitcoin can’t handle the capacity to act as the global currency, not to mention that governments wouldn’t allow it.
Discussion
That's not how it works though.
The current fiat system works on layers to scale it so people can buy a gum ball or whatever tiny purchases. We don't pay for coffee with US treasuries. We use Venmo and all those for little things like that.
This is what the whole Zaps thing is, we can zap a million times a second because of the lightning network and custodial wallets.
Bitcoin itself can handle 9 transactions per second, which is plenty for custodians to settle amongst themselves and other high value transactions. Think of the Bitcoin network itself as the treasuries.