The problem is that we have tons of evidence that rich people actually don't leave because of higher *income* taxes. We even have recent examples like the MA millionaire tax. So the question is why is a wealth tax different? It could be, but I'd like to hear the argument why.
My take on wealth taxes is they won't work well at the local or state level, because you're targeting the people with the greatest means and motivation to just pick up and move somewhere, and they won't work well at the national level, because they'd almost certainly require a constitutional amendment, just as federal income taxes did (the 16th Amendment), so in both cases you're creating a levy that is basically designed to disappear.