Maybe for Sakurai, yes, but not for the franchise as a whole. I'm certain there exist a few candidates worthy of taking over as director, seeing as Kirby has been in good hands since Sakurai's departure.

It's a series that celebrates Nintendo's history that evolves every generation and always, ALWAYS… brings the hype.

I think all other new Smash games just gonna be updated ports of the Ultimate
And the clear reason why is so they could legally keep all characters in the game.