With the billionaires gone, the living standard of the rest of the country will go up. Their money will get spent by more people.
Duh!
When the Billionaires leave, they take ALL of their wealth with them, as a direct result of the Health Insurance Portability and Accountability Act of 1996 (26 USC 877(a)(1)), which claims the right of the United States government to tax the income of former US citizens for 10 years after they have renounced their citizenship and become citizens of another country. So, by taking it ALL with them, all the IRS can do is whine about how unfair they are.
What that means is that they will be spending ALL their money in other countries and funding JOBS in other countries, while the middle class here slips into poverty, as their jobs flow offshore and their tax load goes through the roof. However, you are partially right, in that since their money is funding more jobs offshore, their money will indeed be spent by more people. But, those people will be in other countries.
Just ask the folks in South Africa what happened to their economy as those with money fled their country. The more restrictions they put on wealth and capital flight, the more money slipped out.
The wealthy will always have another option, should their government become too oppressive. They won't suffer, regardless of how oppressive our lawmakers make the laws. It's always those who are left behind who suffer.
According to the IRS, half the US population is paying into the lowest tax bracket now. And that means they aren't making a living.