Bitcoin cannot be used by a certain country's currency for good because if this happens it would be hard for them to be volatile especially when this will be the main currency. Bitcoin will never replace nor change any fiat currency of a certain country just because this bitcoin is not yet supported by the government and also by the banks. People will talk about why it will be changed and also they will always ask where the traditional currency is. Bitcoin will be just an alternative currency until the end of the world, no one can replace a traditional currency.