Still too optimistic on how long-term the American approach will be. There won't be a UBI, the oligarchy will be paid directly from government coffers. The deficit, bonds and other government instruments will paper over the collapse of tax-revenue and population for a while, before the whole house of cards collapses[1]. I think the billionaires hope to be in space habitats or dead by then, if not, there's always their bunkers in New Zealand - their cache of gold bars should still work there after they ravage the USD. Capital knows no borders.
1. See late 1990s Russia. Only simple, extractive industries will chug along.
I don't think they're too smart for that. They're too lazy. They prefer to just gut public health and let disease take care of the culling.
This becomes less of a difficult pill to swallow if a) we're involved in a trade war, b) the economy has crashed and we must work our way out of it "for the country", c) the right people get enough money.
They're too smart for mass murder because that would actually spark a resistance, not to mention get other nations involved. I don't think a sweatshop labor economy will spark a resistance because we can't even resist our current labor abuses (and neither can that segment of China's population).