Won't happen. Scandinavian countries have high tax rates, yet people still become doctors, lawyers and industrialists. That's because limitless greed is not the only motive for working, and 5% of a great deal of money is still a great deal of money.

9 billionaires who plan to give away the majority of their fortunes
http://www.businessinsider.com/billionaires-giving-away-their-money-2015-10/#manoj-bhargava-who-has-promised-to-donate-90-of-his-fortune-focuses-his-charitable-work-on-alleviating-human-suffering-2