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.
Bitcoin is just going to be a currency accepted globally by some part of the global population and even though it makes transaction easy for a lot of people, the governments cannot accept it to be the official currency and would rather regulate it to benefit from it. It is an idea that is already flying all over the world as it makes payment easy worldwide without border effect, and that would make it accessible by those who have access to it, and nothing else asides this.