Governments don't understand cryptos. If they understood fully, they'd be raging lunatics trying to stop it. In my mind, cryptos have the potential to unseat most governmental functions. What will happen to governments when we realize we do not need them?
They will flail, and I'm sure flail harder as things progress and they get a greater understanding of what cryptos can become.
Taxing will never go away. And remember, when you sell your cryptos on an exchange, you generate a taxable event. Using a decentralized exchange, and putting ZCash or Monero transactions in between to anonymize yourself, only works if the vendor you're purchasing from is also anonymous. If they have to report anything to the government, there goes your public key and your anonymity.
Perhaps purchases across border might work for a while, but eventually I'm sure governments will start to cooperate to get this kind of information.
The only way out would be to have a middle man to keep things anonymous. The vendor ships to the middle man, who then ships to you without knowing anything about the transaction or contents. They simply know an address and take possession of the package.
I guess my point is, governments will still be able to collect their taxes, but they won't know how much money people have in the "bank" and won't be able to freeze/confiscate/etc.