But it has already happened.
Bitcoin is serving as an alternative to fiat to people in countries where their fiat currencies aren't necessarily the strongest (suffering from hyperinflation etc.), and also by freelancers and investors as an alternative to fiat.
What he's saying is probably true to them, because let's face it, which central bank would ever want to give up control? Bitcoin probably won't replace fiat altogether, but it'll definitely provide an alternative to fiat currencies which is contrary to what he says.
Heck, they might even come out with their centralized version of crypto. But that's just not the same as decentralized ones like bitcoin, which he is obviously extremely biased about by likening it to a casino, which is clearly a one-dimensional understanding.