I mean it's not impossible, and I think that with technology evolving at a fast pace so does cryptocurrency and the whole market, blockchain will definitely become much stronger and secure in the next decade or so, and it is possible that crypto will be able to replace fiat if the government finds out the advantages of crypto and how it could benefit the economy.
yes, even though the development that you mean is happening, I think it will still be difficult for bitcoin, or other cryptocurrency to replace fiat money, because basically each country has different fiat money, and also different prices.