Indeed, there's no doubt that with the popularity of btc makes it a currency now. Maybe due to it's ease of access for the people and the value that it has. It is becoming a Global Currency, however, if people will focus on btc the currency that they used to have will have no sense or vice versa. Let's face it, bitcoin might be used in different countries in there transactions. But what if btc loses it's value? Will the dependents on btc still have there life back in the way it was before? Btc is still a good way of transaction but it cannot be a concrete currency.
The value of Bitcoin is so higher than the value of a currency, FIAT, should possess.
Bitcoin can becomes an intermediary tool that helps us global transfer money with extremely cheap fees, but to becomes a global currency, the government never accept this situation.
Bitcoin is an unstable system, not only its value is unstable.
You can see just a war in Bitcoin system because between developer have different idea made Bitcoin Cash, created by developers do not accept Bitcoin SegWit, forked from Bitcoin.