No, because governments simply won't allow this.
I also believe this is the main reason, Bitcoin is decentralized, they won't be able to control it.
your answer is somewhat contradictory.
if you say bitcoin is decentralized and they are not able to control it then you are saying that they can not prevent it from replacing fiat since they aren't the ones making the decisions and if bitcoin were to replace fiat, there is nothing the government could do to change that.
I don't think bitcoin will ever replace fiat though because it is not meant to do that. bitcoin is an alternative to fiat not its replacement.