So my question is can bitcoin be a main currency of world economy?
It will become the main currency for crypto economy but not for world economy.
There's a long debate on how will bitcoin going to overtake the currency worldwide but there's a long way to go before it will go there. Dollar will stay and bitcoin will be it's rival and alternative choice for people who wants to stay anonymous.
You have a point besides there are some countries which don't like bitcoin, but maybe in the future it could be possible that bitcoin and dollar will be the main currency of world economy.