A chance? Sure. But it would require willful malicious writing of the bill.

Have you been keeping track of politics AT ALL? You're if fool if you don't EXPECT precisely that to happen. The vast majority of politicians will foam at the mouth at the prospect of passing another tax and then happily add a few provisions to make sure their top donors aren't hurt too much by it. Or do you think it's just a tragic accident that the majority of taxes keeps getting paid by the poor and middle classes?

Across the world, tax rates are largely proportional to health, happiness, and quality of life of the citizens

I don't have any data to prove or disprove that claim, but assuming it's true, then there's certainly better ways to achieve that, like increasing income tax rates on the wealthy. Yes sure, they'll try to avoid it by deferring or offsetting gains where they can, but in the end, whatever they own, they'll still have to convert a certain amount of it to cash in order to spend it, and that can be taxed. No need for such harebrained schemes as taxing unrealized gains.