I can imagine that the new monetary system will be built on bitcoin. I can imagine how people use atomic swaps to exchange between national currencies .
Governments tend to lack transparency in a lot of money-related matters, so countries' reliance on Blockchain (cryptocurrency) as a technology based on transparency will not happen. You can see people or institutions but we will not see countries.
Blockchain technology will be important in civil and economic aspects based on finance and civil companies but will not be a substitute for the current financial system.