If crytpo is decentralized, and if all the governments use it, doesn't it mean, all economies are one? 
Switching from fiat to crypto would fuck everything up, in a good and bad way. And a lot of things can go from bad to worse, I don't really see good things happening. People can do so much corruption and so many things, which blockchain will have the record of, but will not have the record of the person behind it. Honestly, fiat is better. Crypto as good as it maybe, its not good enough for the entire world. Think about it. Just don't arrive at immediate conclusions. There are millions of repercussions and one benefit.
Allowing blockchain technology and the government inculcating it into the system does not mean it would end up decentralized, and I do not see any reason why government will not want to be threading this path in the long run. The idea of giving up control as a result of decentralization is the main threat that is being posed to the government.Switching from fiat to crypto would fuck everything up, in a good and bad way. And a lot of things can go from bad to worse, I don't really see good things happening. People can do so much corruption and so many things, which blockchain will have the record of, but will not have the record of the person behind it. Honestly, fiat is better. Crypto as good as it maybe, its not good enough for the entire world. Think about it. Just don't arrive at immediate conclusions. There are millions of repercussions and one benefit.
In a case where we get to use it an adopt it normally, and the government could find a way to regulate it without any serious challenge or threat posing situations, I guess we can see fiats not being necessary eventually. However, this is just one big assumption considering where the government of each country stands presently.
Yep, we have two sides of a coin here. However, if we talk about centralization and total control over cryptos, we break the main rule of any crypto as they were designed to be decentralized and uncontrolled by governments.