Governments will have to deal with non-sovereign currencies very soon.
You can't wish away such problems as money laundering and terrorist financing by saying, "It can be done using these things, so these things must be against the law. And because they're against the law, they'll cease to exist."
Realistically, the world's governments will need to find a policy that allows for the legitimate use of cryptocurrencies. They will also need to make changes to the way they form and support monetary policy so that their own fiat money doesn't become irrelevant. On the flip side, cryptocurrency issuers will need to provide some means of responding to the civilized world's legitimate concerns about criminal activity.
I wrote a couple Medium articles on this topic.
https://medium.com/@WilliamFreedman/whats-so-special-about-being-sovereign-f64a6765a7f4https://medium.com/@WilliamFreedman/poor-misunderstood-bis-needs-a-hug-28c92a5de99d