Worth noting that several dual-citizenship friends have, over the last couple years, renounced US citizenship for tax reasons in each case. Very little appealing about being a US citizen for the very rich.
What this article fails to note is that the last thing the very wealthy want is a new form of citizenship or new country. Being a citizen of any given country becomes more like selecting the clubs you belong to based on the value-added services they provide. Starting a new club is a headache. There are plenty of reasonable ones out there.
And for the most part these clubs are already run by the super rich. The rest of the citizenry is just mowing the lawns as far as they are concerned.