They won't flee. The tax would have to astronomical to offset the advantages of doing business in the US. If that wasn't true, they would have all disclaimed their US citizenship and moved to Monaco already.
For the record, I’m not necessarily opposed to the idea of taxation on the wealthy, but I want to understand why having no rich is better for everyone.
Extraordinary claims, etc
I'd also note that I would prefer to adjust tax/accounting laws to prevent the accumulation in the first place, not just roll out a blanket "take everything over a billion-ish law" as that feels more like a band-aid than a fix.
Yes, I agree with this one. Some sort of reform on estate and inheritance is long overdue.