Have you lot seen the trading volume of BTC? Nevermind the altcoins? Trust me, if they're going to make cyrpto currencies illegal they're going to have a hell of a fight on their hands, I'm pretty sure we're going to see a very similar set of events to what filesharing is going through.
The problem is that people have to be willing to violate the law (and by that I mean just use BTC anyway, and possibly go to jail for doing so) in order to bring about change. It worked for the Civil Rights Movement in the U.S., it's what would work now. But no one in their right mind would do that because they rightly fear having their lives ruined with no one to support them because everyone else would mindlessly do what the government tells them to out of fear for their own lives.
I honestly never thought I'd live to see freaking FASCISM of all things rise up in my lifetime but here we are.