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?
No, it can't be, since all economic activities should be strictly regulated in order to avoid abusion by the market players of the rights of all other players.
Bitcoin and cryptocurrencies in general do not provide that centralized instrument of control - their intended use is exactly the opposite (deregulation and freedom of business and finance).