It will never happen, most people continue to use government currency and it will stay like that. Crypto will always be a minority. I think people become too blinded by what average people do when they spend time on a niche forum like this one.
We also have to consider that many gambler still want to play on a traditional way and of course thats playing online using fiat money. The government will always support that kind of business because they will earn on that, though crypto gambling are also growing I still see this one just an alternative for a gambler who know how to use cryptocurrency.
The trend of gambling with fiat will decrease day by day as it is easy to gamble online using crytpto. This does not mean that physical casino will stop operating but they may also introcude the payment by bitcoin and other crypto curenices. Traditional gambling will exists but with new mode of payment i.e crypto currenices.