This was the third time Sakurai has been brought back to do more Smash after apparently finishing with the series. Sure it's a lot of work, and Sakurai's work ethic seems second to none, but while he obviously must feel ownership over the series, he dropped Kirby, so I suspect if he truly wasn't enjoying himself, he'd opt to work or not work elsewhere. He's not so shortsighted as to know eventually the series will carry on without him.