Unless the problem of Bitcoin's high volatility is solved, it will never could replace dollars or FIAT.
I doubt the context of OP referred to Bitcoin as a replacement to fiat or the dollar.
Something we need to understand is that, the fiat is not just a currency, it’s an identity, a mode of doing businesses within a locality and across borders. You ain’t going to through all that in the wind because of a highly volatile or unstable Bitcoin.
What is a government without control, fiat brings the government that control and it is accessible to all unlike Bitcoin that is accessible only to the internet and gadget enabled population.
While Bitcoin might help by some means, it’s not the savior of our economic crisis. The world seems to be growing faster than it’s producing and we need to reverse that.
For me personally bitcoin is an asset to benefit at the moment of bullrun, but if you talk about whether bictoin can be a savior as something that will benefit us when the economy slumps, of course it is not illogical if with prices and fluctuations according to market demand, people will not run there, they need to save their money if the economy slumps globally, and when the decline is in its phase is the right time to buy bitcoin, because then we will return why the original trend.
Bitcoin will save us if we buy at the bottom price, when everyone is scared to keep their money in bitcoin.