Bitcoin has no doubt that it can be a global currency in the future. Its features are well established and can really cater to the fast changing technology that we are experiencing right now. But knowing its decentralized, i think it will find a hard time getting its approval from most of the countries' governments. Althought there are already quite number of countries who are thinking to adopt it later on, but there is still no guarantee that it will certainly happen. While fiat will always remain as a main currency, but crypto or bitcoin's future is still uncertain up to now.