Probably near the end of their lives, some have said they would do that.
But generally I think an altruistic Billionaire would donate to various organizations, groups, and individuals.
People say billions is a lot but when you divide it up amongst Billions of people, it’s goes down to dollars, or pennies.
You at best could give 200,000 people $5,000 each, is a lot maybe, or maybe not.
You can fiddle around more money to fewer people, or less money to more people.
Billions is a dent, which is why we trillion dollar level budgets for everything major in The United States.