Bitcoin is used more and more in time to lead to the knowledge of people for bitcoin, but bitcoin can hardly become a currency in one country due to its instability and not security. People will think that some kind of fraud and plagiarism are, but the risk of losing their wealth in bitcoin is also high.
I think bitcoin need more maturity and time to grow. Once the bitcoin price is stable and everyone is comfortable to accept bitcoin as a payment method only then is the time when we can see bitcoin really becoming the main stream currency.
That would be the time when we will say that bitcoin is the one world currency.