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.
Maybe it will happen if the crypto currency is getting famous but Bitcoin will still be used in the future. Because if Bitcoin disappears from market or from the crypto world it might shake the crypto currency world. So from that, even though Bitcoin is called the mainstream, it certainly will still be used.