The average tax income from billionaires in california looks to be around 10million a year. So combined the about 200 billionaires in california are paying 2 billion a year. Rough numbers would be that is 150 of them left then the one time tax would start being a negative income in 10 years. That assumes money stays flat.
Honestly there is no way that this ends up being a serious net negative and these folks are still operating in California enough that they may fail to avoid residency review.