That is definitely the big question. Given that Gates is busy donating most of his cash to charity, there are counterexamples.
But even biting the bullet and accepting the premise, it’s not immediately obvious that losing all of the work from current billionaires would be a bad trade in exchange for substantially reduced inequality.
My counterpoint is that most billionaires don’t seem to be continuing to work hard primarily to get another billion. It’s more for the fun/fulfillment and status. If they can still have fun and status even without controlling as much wealth they will probably still go for it.