According to Brian Armstrong, the chief executive of coinbase, the number of users of cryptocurrency is going to increase by 1 billion in about next 5 years. Everyday the field of cryptocurrency is expanding and the number of cryptocurrency users are also increasing in the same rate. He believes that the growth will be caused by the growing number of cryptocurrency companies. There is a big probability of this prediction coming true as the cryptocurrency market is actually expanding everyday.
While this is still unpredictable. As Satoshi Nakamoto said at one time - in twenty years there will be either a lot of transactions in Bitcoin, or there will be no transactions. Maybe in the next five years, a billion people will use the cryptocurrency. Despite many predictions, no one can know for sure.
Just like the creator said, Satoshi is not also sure about the mass adoption but since we are slowly showing a big support on cryptocurrency, i think we can achieve this. We encountered many problems before and yet many new investors are coming and the volume is increasing. Predictions can still happen, lets not expect much.