No, or at least not in any materially different numbers than today. The United States already has a little known but quite important wealth tax: the U.S. Expatriation Tax.
I'm a U.S. person living in Singapore, and consequently I am subject to both the U.S. and Singapore tax systems. In practice what this means (oversimplifying only slightly) is that I pay Singapore first, then I pay the U.S. the difference. (The U.S. tax rate is generally higher.) I'm not "double taxed" -- that's a common and inaccurate mythology -- but I am partially "trued up" to the U.S. rate. My net effective tax rate ends up in between the Singapore and U.S. rates: higher than what a non-U.S. person in Singapore would pay, but lower than what a comparably situated U.S. person in the U.S. would pay.(*)
A proposed, more generalized U.S. wealth tax presumably would slide right into this system. That is, wealthy U.S. persons living in Singapore, or anywhere else, would still owe and pay the general U.S. wealth tax.
OK, so what if they don't like that? Well, there's a solution: they can visit a U.S. embassy or consulate such as the one on Napier Road, pay a US$2,350(**) fee (the cost for a Certificate of Loss of Nationality, Form DS-4083), and irrevocably and permanently terminate their U.S. citizenships. Eduardo Saverin, one of Facebook's co-founders (a citizen of Brazil and a Permanent Resident of Singapore), did exactly that. Unfortunately for him and for others there's a big catch: the U.S. Expatriation Tax. Oversimplifying only slightly, if your global net worth is US$2 million or more, then you have to pay immediate "mark to market" capital gains tax on your total global wealth as you terminate your U.S. citizenship. Moreover, if you have a loved one who retains his/her U.S. citizenship (or acquires U.S. citizenship), you can still leave your estate to that person, but the U.S. estate tax flips to a serious U.S. inheritance tax for that heir.
That's extremely unlikely.
I can imagine that: almost none. One reason is that billionaire founders already don't do this even to fund their day-to-day living expenses. What they do instead, quite often, is they obtain secured loans using their stock as collateral. Interest rates on secured loans are low, and they can defer the capital gains tax. Then they keep increasing the outstanding loan amount, which they can do for their entire lives since they're so immensely wealthy. That's exactly what they'd still do to pay a hypothetical wealth tax, also because they don't want to lose voting power.
There's also something called a charitable remainder trust which many of them do. The idea here is that you irrevocably donate some of your stock to, say, Harvard University. The world's wealthiest university is, technically, not-for-profit and, according to the U.S. tax code anyway, treated the same as a charity for these purposes. Harvard then manages the funds during your lifetime, pays you a regular annuity, and then keeps the remainder when you die. (There are some rules about the amount of the annuity and how it's taxed.) And the tax benefits to this arrangement are enormous, plus you can often get your name on some piece of Harvard real estate and get your favorite 18 year olds admissions into Harvard. (Harvard is careful not to
guarantee admission, but if the donation is big enough or bigger and your favorite 18 year old can read and write decently enough -- highly likely with the extra high school tutoring you can easily afford if need be -- wink wink, she/he is admitted.) It's quite likely the tax benefits will be even more enormous with a hypothetical wealth tax, which helps explain why charities and universities generally like the idea, albeit quietly lest they offend their wealthy donors.
And I'm barely scratching the surface, but suffice it to say that a general U.S. wealth tax along the lines Senator Warren has proposed would highly likely be an effective revenue raiser, comparatively hard to avoid and evade, highly cost effectively collectable, and highly non-distortionary. I haven't looked closely at the wealth tax Senator Sanders has proposed, but I'm not giving it much attention purely on political grounds since he's currently polling in third place within his adopted party's presidential nomination contest.
Another factor is that, ceteris paribus, a wealth tax would encourage those subject to it to spend more on goods and services in the here and now. The boost to consumption would
stimulate the macroeconomy. Of course government can spend too, and higher tax revenues would support more government spending, ceteris paribus. Broadly speaking, the candidates proposing wealth taxes also have "high multiplier" (high return) proposals for spending, which would also be short-term and long-term stimulative.
I think you've got this exactly backwards. You might or might not oppose wealth taxes for other reasons, but negative effects on the macroeconomy isn't a good reason. It's rather the opposite. Right now most tax systems comparatively discourage the movement, the transmission of wealth and comparatively encourage a static hoarding of wealth, at least for tax deferral if not outright tax avoidance. A wealth tax helps to mitigate those generally perverse incentives, and economically speaking that's not a bad thing. And selective wealth taxes are ancient, notably property taxes (which Singapore has). Property taxes are wealth taxes, too.
(*) Don't weep too much for us U.S. persons, though! Let's suppose instead I work in Belgium. Belgian income tax rates are generally higher than U.S. income tax rates, so the smart play there is to skip IRS Form 2555 (the Foreign Earned Income Exclusion) and take only IRS Form 1116, the Foreign Tax Credit. You're allowed to do that. Then, at some point anyway, spend a little time working in the U.S. again. What happens then is that you get to "bank" up to 10 years worth of the difference between the higher Belgian income tax rate and the lower U.S. income tax rate. Then you can spend down those banked credits to offset your future U.S. income tax in the same broad income category. No other country does this, and it's the sunny, happy side of U.S. tax personhood. Imagine the Singapore government reimbursing you, in the form of lower or zero Singapore income tax, after you come back to Singapore, after a working stint in Belgium, or Japan, or Australia, or Norway, or some other generally higher income tax jurisdiction. However, I like Singapore, thanks. Not everything comes down to money, thank goodness.
(**) The U.S. government charges "cost recovery" for services such as this one, and that US$2,350 amount probably is approximately correct in terms of the actual, average cost to the U.S. government to process one of these exits. I don't think U.S. consular and immigration services -- or most other government services -- should be charged on a narrow cost recovery basis. Such fee burdens are regressive, and I'm against regressivity. But if you're going to levy fees this way across a broad range of government services, it's only fair to apply that same fee rationale to exiting U.S. citizens too.