They may become a target for criminals, but governments - I am not so sure. Most of these millionaires and billionaires would have highly paid lawyers who would be able to move their wealth offshore. In any case, unless you sell your bitcoins and incur capital gains, your crypto wealth really isn't taxable.
Of course, the criminals will really not care about that.
Governments these days are not very much different from hard-core criminals, and I'm afraid they have never been. You may want to take notice of what Edward Snowden says about NSA's extensive involvement in the targeted killing program or read what Hillary Clinton wrote in her leaked emails when she was a state secretary. When you become a nuisance, a pain in the ass, highly paid lawyers won't help you. You would need heavily armed bodyguards then. And a place where they won't be able find you since bodyguards may not help you. Puerto Rico obviously doesn't cut it as a safe haven.