No, cryptocurrency can only occupy a certain niche in the financial sector. Moreover, it is not capable and will never dominate the currencies of states. There are other factors, taking into account which the cryptocurrency is not able to displace the national currency of states. First of all, it is its high price volatility. The lack of certain stability makes it impossible to use it as a means of payment. On the part of states, its decentralization nature is unacceptable. They can allow decentralized cryptocurrency to circulate, but they won't support it.
Also, they will never give up their currency, since it serves the country's economy, and cryptocurrency cannot do this.