The tax man may be avoidable at first but in the end he will get basically every cent he feels he is "due". Nothing is certain in life but death and taxes and that doesn't appear like it's going to change any time soon.
Governments are going to be clamping down on anonymous purchases/trades in the crypto space, mainly by targeting the fiat entry points such as what is taking place in South Korea right now. Next they will likely start gaining access to various major centralized exchanges to get trade information on the various users of these platforms (similar to what took place with the IRS and Coinbase a few months back). And finally the last wave will be to directly target privacy coins such as Monero/Verge/Nav... as those will become the final tax-haven left standing, and they will target them in a way that centralized exchanges will de-list them and people will only be able to buy/sell them on a peer-to-peer level through a decentralized exchange, but even then the holder wont be able to sell them for fiat or trade them for other non-privacy coins very easily or on any major levels.
All this should not be unexpected as its quite blatantly clear how this is all going to play out. Governments will allow cryptos to thrive in the long run, but not without cementing their ability to collect what they feel is due (taxes, taxes, and more taxes...).
What you're saying is right, Governments will find ways to tax cryptocurrencies one way or another. But two things could happen, firstly governments could render cryptocurrencies worthless due to over-regulation, in other words destroy the reasons why these are so useful i.e. privacy, low fees, real time, etc. thus destroying the blockchain world. Or they will hopefully realise that cryptocurrencies do provide a useful service and so they strike a reasonable balance between regulation and freedom. There's a third thing that is already going down the gurgler, governments could do next to nothing. But this won't happen.
Hopefully governments will find the sweet spot which enables cryptocurrencies to flourish and perform while keeping officials happy. I'm holding my breath but ...
Thanks for mentioning NAV. Remember, they are located in New Zealand, historically one of the hardest nuts to crack for tax authorities. They are also working on seamless encrypted exchanges between coins and fiat. Read between the lines and you'll see the NAV team basically agree with you on what's coming and is preparing.
No prob, NAV is a decent and mostly overlooked privacy coin at the current time. I personally avoid privacy coins but that is just me, to each his own I guess. BTW nice Q quote. :D