The recent exposé about the Trump family finances shines a light on the ways in which the wealthiest Americans can avoid estate and gift taxes on the transfer of assets to their children.
https://www.nytimes.com/2018/10/11/opinion/trump-bezos-estate-tax.html?action=click&module=Opinion&pgtype=Homepage"Like Donald Trump, many of the Forbes 400 acquired some or all of their wealth from their parents. These transfers of wealth pass entirely free of income taxes."
The measure of a well-functioning democracy is a tax system that fairly apportions its burdens.
Can blockchain and the inevitable virtual economy make the taxing system less disproportionate?
They could do this by issuing closed source currency, but then again, most transactions are already digital, it just lacks an open blockchain.
As far as taxing foreign currencies and neutral ones like bitcoin, I don't see how, they can only tax exchange deposits.
But the wealthy will always have resources to circumvent taxes. They can hire the best accountants and lawyers in the world and find ways to avoid the cut. Also in some countries taxes are nonsensically high which only incentive that behaviour.