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.
I would find it very hard to believe that by the year 2022 everyone will be using bitcoin. but i also would not be surprised to be wrong, given the remarkable pace at which bitcoin has already advanced. I would say that by 2030 all governments in the world will be holding bitcoin and lightening networks will still allow everyday transactions also.
I think it would be very difficult for bitcoin to have users all over the world in the very near future, I doubt even though 10 years to come. bitcoin development takes a long time #IMO