If bitcoin or some other crypto currency becomes the default money in the future, that means it doesn't have to be compared to the dollar. And I am not sure about the government taking my money away just because it is something that's online or digital. In many ways, the government ain't that smart, they are only good in taxing us until we bleed. So, I am not really afraid if the time comes that every money you have is the crypto currency kind because surely security features would be upgraded tenfold if that becomes the case.
Plus, I don't see how the government could get a hold of a persons bitcoin unless they torture the person enough to get him to give up his cryptographically secured private key....I mean, that's more secure than cash in my opinion. If it were cash, all they'd have to do is kick in the door and take it....but with bitcoin they'd have to pry the key from the resources of their victim's mind....A person could always run to another country, carrying his private key in his mind, wearing nothing but the clothes on his back, and still recover his money. It's safer than cash! Try boarding a plane with a few 100k in cash and see how far you'd get....and that will get even harder once the cash is finally fitted with RFID tags.
Things don't work the way you fantasize
The government agencies typically don't need to torture anyone. There are a lot of ways to make people reveal anything they might know (including their private keys). If they have families (and almost everyone has a family, I mean, at least, a dad and a mom), it is just a matter of making the lives of their dear ones somewhat less pleasant, and all private and public keys are surrendered in less than no time. If you really want to be the guy you portrayed in your post, you should be an absolute douche bag internally, with a heart of stone and no soul altogether