What countries are they moving to? Currently if you save and invest your money you can pass it to your children (or whoever) with a step up in cost basis. So the investments can go on indefinitely from generation to generation essentially without tax. Because technically, you haven't realized any gains yet. In the meantime, you can borrow from banks against these investments (also I believe not taxable, at least not like income tax). These new laws would get rid of the ability to pass on your wealth without a significant (like 50%?) tax because they would recognize death or gifts as a taxable "transaction". Unless you donate it to charity. Which might be why Buffet is leaving all of his money to charities (which are run by his kids...or at least some of them).

I'm honestly still trying to figure this out but that's what I understand so far. Another interesting consequence is that calculating long term investment cost basis's sounds like a f'ing nightmare. Maybe that's why the step up rule exists?