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.
Yes it will become the mainstream someday, I fully believe in that. As you can see and analyzed, the volume of bitcoin and other altcoins are increasing very high as the time passes. So we can conclude that as long as the time passes and the news of bitcoin keep spreading, the more people and investors used this as a mode of payment. We can see that on other companies now accepting bitcoins and other altcoins. So it is just have a matter of time to become a mainstream.