it is very difficult for bitcoin to become a global currency. because there are still many people who do not know bitcoin and there are still many countries that prohibit the existence of bitcoin. because they fear that the development of bitcoin can not be overcome. but you do not have to worry though some countries do not allow it but in some countries, many have received and legalized bitcoin. and I'm sure bitcoin will go on and on all over the world.
It is not right, bitcoin will be global currency although it will take long time to take over the market but it is doubtless that in the future the whole world will use only bitcoin as their regular currency even in their local markets. Nothing could stop bitcoin now from prevailing in the world. It will be the global currency because the aim is to hold the market.