$108B net worth now (per chart in the article), so he will be left with paltry $1B.
Still, would be beautiful to see all megarich do the same. Keep a few yachts, mansions and planes if you give back a few small countries' worth of GDP back.
Apparently billionaires in the USA hold 4.48 trillion, 756 of them or so.
So if they all dumped their wealth and saved a billion (should be enough to retire on, even for the conservative portfolio!) we would have 3.72 trillion - it would cover the US deficit for two, maybe three years.
Or to spin this another way: Americans spend around $200B* annually on education (private spend, on top of federal/state/local education spend), so this would provide all-expenses-paid free tuition for everyone for 18 years, or more than 50 years if focusing on primary/secondary education. In that time, there might be a new crop of megarich to continue the cycle :)
([*] $50B for primary/secondary ed, $150B for higher - figures via Kagi Assistant, which I didn't double-check).
Still, would be beautiful to see all megarich do the same. Keep a few yachts, mansions and planes if you give back a few small countries' worth of GDP back.