The question is, will governments agree to it? George Monbiot address this in the Guardian, pointing out how billionaires have used their wealth to corrupt democracy, and as a result, governments tend to serve them rather than their voters:
Every so often, UK governments promise to act, then deliberately vitiate their own proposals with loopholes wide enough to contain an oligarch’s mansion. When poorer countries propose global initiatives to prevent the ultra-rich from escaping taxation, rich nations, including the UK, have sought to stop them. They do so not in response to public demand, but in response to pressure from a tiny proportion of the population – billionaires, the newspapers they own and the concierge class that works for them.I'd put it more bluntly: a government which refuses to tax billionaires is a traitor to its people. And we should treat them as such.So here’s the test the G20 governments face: 3,000 versus 8 billion. Do their loyalties lie with 0.00004% of the world’s population, or with the rest? If your government seeks to block the Brazilian proposal, you will have your answer.