Unless like Crypto States of (insert nation) was made some day and that would be possible which is impossible, hmm? 
Crypto wouldn't work to replace in fiat. It has been discussed already quite a lot. Many incidents already happened namely: Mt. Gox, Coindesk in Japan, EtherDelta DNS hack, and yet people still expect that government will expect to fully replace their respective currency into digital ones. It is innovative but at the same time it could also prove destructive in the economy.