Probably That may happened within 8-10years. With Due respect, Let you know that If ETF get approved for bitcoin, then bitcoin will be more polupar & trusted than now. Although many countries does not accept crypto as real money but nowadays world is being digital as well as many countries already does unrestricted bitcoin. So it's not impossible that world will accept crypto as real money.
And the question is, would they ever approve it? They understand the benefit of bitcoin to them and their economy, but the thing is, they cannot have their cake and eat all, bitcoin replacing fiat will completely collapse the dollar system which the United State has been using as one of the tools to remain strong and relevant in the market and despite that their fiat even does more harm in terms of corruption than cryptocurrency, they would not want to fully approve it.
So, what you see them do is just to remain silent over it and allow the bitcoin to play by its own rule, and seems satoshi already knew this too, that is why he created a system that will serve as alternative to fiat and not a system that would replace fiat completely, we are just the ones making it look like it would replace fiat.