According to a study conducted by researchers at Imperial College London, cryptocurrency has the potential to become a form of payment that is widely used for decades to come. In their research report entitled "Cryptocurrency: Overcoming Barriers to Trust and Adoption" Professor Imperial College London, William Knottenbelt, and Imperial College Business School Dr. Zeynup Gurguc, argue that cryptocurrency has so far acted as a store of value like a fiat currency.
No currency is the mainstream all over the world like in India Rupees is the mainstream and in USA dollar is the mainstream but Bitcoin can become the common currency between all the countries... and already almost everyone is using Bitcoin now a days so we can consider that Bitcoin has become already the mainstream and the common currency all over the world except the countries where Bitcoin is banned.