Of course, Bitcoin can be a world currency. However, Bitcoin is not valid in all countries. But seeing the popularity of Bitcoin,it will be the world currency for a time.Only the bitcoin has been known in all the countries, which could not make any other coins.Everywhere they are Bitcoin,world Currency Will be.
Bitcoin is decentralized money bro until it makes the bitcon as a legal money. You will find the bitcoin price to reach more than 50k USD in 2020. That time you will see the bitcoin has been adopted by the many countries dude.
So that you itself bitcoin is global currency. If you get into the Japan airport, even now itself you can access the bitcoin ATMs at there and can legally used.
Moeover if we talk about currency, it is about what people are using, and as stated a while ago, bitcoin will reavh its 50k USD in the near future. This only means that bitcoin will be more popular, and popularity is because of the people using it and those people are the reason why there are currency. That is why the bitcoin is indeed a global currency soon.