Basically bitcoin is the media which's more appropriate and can comply, with various aspects of banking and finance rather than currencies supported by central banks, especially for those who don't have bank accounts and small-scale international trade players. On the other hand, bitcoin's able to combine the principles of social benefits, positive externalities and we can also make it as opposed to the risk of shifting values. The presence of Negative Effects will usually be found as time goes by.
Still possibility of making crypto currency particularly bitcoin as the universal currency because every nations will protect its own currency since it will determine the status of every country, but still I believe that somewhere in the future it will happen when blockchain dominate the entire digital technology.