So my question is can bitcoin be a main currency of world economy?
I'm sure that there is a future for bitcoin. Already, there are places where bitcoin is accepted as a means of payment, and I think there will be more of them when it will be possible to conduct micropayments. But before Bitcoin becomes the dominant global money, it will have to successfully pass the development stage, where scalability and privacy issues will be resolved. It is known that the increasing complexity of computation requires developers to create a carefully thought-out approach, which is necessary to solve the problem regarding the optimal block sizes. Otherwise, the Bitcoin system can split into several parts or get protection problems.