Do not expect too much while not all countries are supporting crypto as a currency. Maybe it may happen in a country where the governement supports crytpo and online gambling, but to see it worldwide is still like a day dreaming at this moment. I do not mean to underestimate crypto or cryto gambling, just looking at the fact about it.
I think we should just get it straight to our heads that fiat payment will be there for live because everyone cannot know everything about crypto, there. There are a lot of people that still have little knowledge of cryptocurrency and it would take many years or even a lifetime to educate them on this. Let's just say for now that it will be very difficult or rather it’s impossible to have only crypto as the only method of payment.