If it were the case that the main currency of every country in the world is Bitcoin. Then how do you think the world economy would be run? Because when Bitcoin becomes the main currency, the American dollar and other countries will have Bitcoin as their main currency. The local currency of that country will be associated with it as the second currency. In this case, how would Bitcoin be used or how can it play a good role in the world economy?
How do you think all of these is going to happen? Why will the government relish their local currency which they have absolutely control over for a currency such like bitcoin that they can't control as it's not centralized as fiat. While I believe it's going to be beneficial for the community should this happen, I do believe that bitcoin has already or is playing it's special alternative role already like the gold, silver and other precious metals. Government can still hold it as national reserve while they still have control of their local currency.