This is why millionaires keep their money in offshore bank accounts, or precious metals like gold, or priceless/expensive paintings/artifacts etc etc.
Offshore bank accounts are no more solution after FATCA. Every USD transfer can be stopped by US intermediary bank. Many offshore financial companies are investigating bitcoin potential right now.
But rare antiques, exclusive real estate, gold and resources are still good way to save your wealth.
Well Bitcoin if stabilized it would be a great means of storing wealth and using it offshore. All an offshore financial service has to do is implement a system like Protonmail that has 2 passwords one that both the customer and company know which lets you access your account on their servers, and one that only the customer knows which decrypts your account on their servers. This would protect a US citizen as they can plead the 5th, and the offshore financial service company is safe because they don't know what their customers are doing, in short, your privacy is backed by cryptography, not 3rd parties that can be subpoenaed.