Now we can see some countries are regulating bitcoin and some government don't like it.Otherwise Bitcoin hasn't a stable price.
So my question is can bitcoin be a main currency of world economy?
It is hard to make bitcoin as main currency in the world because every country have their own advantages and regulation on their economy. But if most country in the world regulate bitcoin, I am believe bitcoin can accepted as payment in merchant in every country beside their official fiat currency.
Yes, if bitcoins have been accepted in different countries and used as a medium of exchange other than their currencies, I'm sure that for countries that have not set bitcoin as a means of exchange they will do the same to make bitcoin as a medium of exchange.