It is said that bitcoin will destroy the fiat system but i believe that if this happens the world will change completly because banks and a lot of things will go out of market.
Bitcoin will not destroy the fiat but will be an alternative currency in the future. The users of cryptocurrency will increase but the percentage of users will vary in every countries exposure to internet. The utilisation of cryptocurrency as a means of exchange will mostly concentrated in the City where most business accepted legit cryptocurrency as payment.