Central banks are not going anywhere, because governments need central banks since they are the ones who give the government money, not Bitcoin.
Bitcoin would be good in a libertarian-run country, but this is not the model with which any country operates in right now, so you have to work with what you have, and Bitcoin is an impractical option for many governments' finance ministries.
Bitcoin is one of the best investment in the world right now and the best crypto coin, Bitcoin has really made some investors rich and has increased the economy of the world, Bitcoin can never overthrown the central banks of countries as I'm speaking to you there are countries that has not accepted Bitcoin to be used in there country and has even made it illegal and if caught using will be arrested and prosecuted.
The function of central banks of any country is different and can never be performed by Bitcoin, the central banks of countries are responsible for printing money,
Bitcoin can function in a particular way and can be used as a means of payment.
Bitcoin should be accepted as a means of payment, some countries has already made it legal and has started using it as a means of payment and it has helped to develop and build there economy,
The reason why some countries has not accepted Bitcoin as a form of payment is because they see Bitcoin as promoting crime for example if you make a transaction with someone using Bitcoin and may later they want to fine the person you made the transaction with you can not find or track down the Parson Because of the way crypto functions no trace, no identity can be discovered.
And also some countries feels Bitcoin will destroy or bring down there economy.
Bitcoin can never replace central banks of countries because it can't perform it's functions.