Commonwealth bank of Australia is already embracing crypto trading, one of the biggest banks out there probs. Miami & NY are working on city coins for their communities and there's alot of countries/cities trying to catch up with the wave - shows significant signs of mass adoption imo and it's only going to get better over time. Cryptocurrency replacing fiat would be the most difficult challenge though, no government wants to lose control over monetary values. I think they'll end up making regulations for it eventually as they always do, just to keep their hand ontop of everything.