He actually hasn't shown what he will do with that money or similar money in the future. He could declare that it would mostly go to charity or political causes, which is what the New York Times Editorial Board wants him to do, but he has not done so.Also, people who criticized Obama for the $400k speech fee are looking like busters, now that Obama has actually shown what he was gonna do with that money.
Because Clinton released her tax returns, we know that about a little less than 10% of their income from speaking fees was donated onward. If the same proportion were followed, that would mean donating $40,000 of a $400,000 speaking fee.