Fiat will be replaced by crypto currency but i dont think it will be bitcoin. Government want to control everything and even fiat money , bitcoin cant control by the governement so they will create thier own and will use blockchain technology to make a new way of payment before fiat currency fall.
Governmentcoin will be fully digitised fiat. There won't be any difference in its fundamental nature, only its implementation. Their absolute control over it, and you, will make it more worthless with greater rapidity and make a stronger than ever case for Bitcoin.
This.
Government will do what it takes to level their local currency the same as BTC. They're gonna innovate on how money flows inside their country. Besides we already have credit cards/debit cards that is somehow a bit similar to what BTC can do except that it is fully regulated by banks as well as the government through fees/taxes.