Although he hasn’t clarified in what capacity.
Super Smash Bros. is coming to the Nintendo Switch, which is great news- but we don’t actually know a whole lot about this upcoming game. For instance, is this a new game, or an enhanced port of the Wii U version? What is the roster for this game going to be like? And most importantly- is series creator Masahiro Sakurai going to be working on this title?
That question is actually a pertinent one, because Sakurai has stated his distaste of working on large AAA projects, and sequels, multiple times previously. He has also, with each Smash game following the original, stated that it will be his last one (although he always returns for the next one- much like Hideo Kojima used to be with Metal Gear).
Apparently, that has happened again, because Sakurai has confirmed that he is working on Smash, although he has declined to comment what capacity he will be working on the new game in. Hopefully, he will delegate more this time, to avoid being burned out like he usually gets. Super Smash Bros. is due out exclusively on the Nintendo Switch some time later this year.
— 桜井 政博 (@Sora_Sakurai) March 8, 2018