What will happen to the billionaire oligarchs is the same as happens now:

• Warren Buffet goes to an investment bank and says "I want a $100 million line of credit for pocket money"
• Bank asks "what collateral do you have?"
• Warren Buffet: "$XX billion of Berkshire Hathaway shares"
• Bank: "ok we will give you a $100 million line of credit using your shares as collateral, to be repaid upon your death"
• Warren Buffet uses that line of credit for everyday spending until he dies. He pays no capital gains tax on this money because he hasn't sold any shares to obtain it.
• When his heirs inherit the shares the cost basis of the shares is adjusted to current market value
• Buffet heirs repay the line of credit by selling shares
• Buffet heirs pay almost no capital gains tax because they're essentially selling the shares for the same amount as their adjusted cost basis