central banks not surprisingly show concern for their eventual extinction (as will happen as the currency becomes distributed and there is no need for a middle man (a central bank). i believe, at some point, depending on their grip on the government they can orchestrate the outlawing of the use of cryptocurrencies (example: China, Vietnam)
sept 4 2017 https://www.coindesk.com/china-outlaws-icos-financial-regulators-order-halt-token-trading/
oct 29, 2017https://tuoitrenews.vn/news/business/20171029/vietnams-central-bank-outlaws-bitcoin/42300.html