If the global economy continues to deteriorate, do you think central banks will collapse? If that happens, it will be the end of Fiat for good. In such a scenario, do you think Bitcoin will become the currency of the world?
the economic downfall of a country will certainly have a significant impact on the central bank, because policies relating to fiat currency are related to this institution. but even so, a country's economic downfall will not eliminate this institution, because as long as a country has a currency they have a central bank that regulates this.
and in the worst case when the central bank is in a crisis phase, bitcoin will not become the world currency, because the government will not allow that to happen. maybe they will launch a new currency with a new system, because they don't want to lose control over their citizens.