This is an inevitable event that is bound to happen. As humanity emerges into a more technological world, the status of monetary affairs shift to cashless and this is spearheaded by Bitcoin. Some countries like South Korea has taken a lead in the legalization of Bitcoin as a currency and with time several countries will follow. The presence of Bitcoin in a country brings both financial satisfaction and job opportunities thereby enhancing the economy of the country.
The currency of a single country can not be bitcoin in principle. No state will commit such stupidity and does not recognize it as its main currency. Such an act would quickly destroy the economy of this country. Bitcoin and other crypto currency are only able to walk in parallel with the national paper money of the state, and no more.
South Korea, as far as I know, recognized bitcoin as an asset, and not as a means of payment. As a means of payment, that is, as money, bitcoin is recognized in Japan, Germany, the European Union is also considering the possibility of recognizing crypto currency as a means of payment.