There is zero percent chance Congress will pass legislation to tax unrealized gains. Most billionaires earn relatively little INCOME subject to federal income tax. They make their money via capital gains, typically taxed at 20%. Need to pass legislation to make Capital Gains taxes progressive, increasing the Capital Gains tax rate as their gains rise. And remove the cap on earnings subject to social security taxes (currently capped at $168,600). These are feasible changes to the tax code.