It could be possible but not eventually. There would be many things to consider for it to become a global currency.
Bitcoin now is able to used in an international currency but it can not spend it in offline method because there is not real coin as this moment, but i think bitcoin now is global currency which can be use it in online method.
First, Bitcoin needs to establish itself as a "currency". Right now only 2 or 3 countries recognize Bitcoin as a form of currency. The usage is also quite low, and daily transaction volumes amount to less than $10 million USD. Compare this to the forex volumes of hundreds of billions of USD for the major world currencies such as the US Dollar and UK Pound.
Bitcoin still need to be more famous, in order to become a global currency, for now its still too little user know bitcoin and using bitcoin as transaction, and bitcoin still need to develop to upgrade the transaction speed, so it's still a long way to become global currency