A New Smash Bros. Would Need A Smaller Roster, Admits Sakurai
Article : https://www.nintendolife.com/news/2021/12/a-new-smash-bros-would-need-a-smaller-roster-admits-sakurai
I'm probably not the fan of choice for Sakurai himself to have feedback from, but again I think he should consider either continuing SSBU with making Fighters Passes every few years, or make a Smash Bros game that's promotional with another video game company, preferably Sega.
Option 1. Continued Fighter Passes.
From what I understand, I believe Sakurai regards each Smash Bros. game like an "ecosystem". I believe when he introduces a new fighter he puts heavy consideration in not only the fighers movesets and stats but how that fighter will play well on various stages, how that fighter is balanced against other fighters and how other fighters in the game match up well to the newcomer. That said it's understandable why it would be difficult for Sakurai to come up with new fighters every few years for SSBU.
But would it really be more easier to make a new Smash Bros. game over additional Fighter Passes for SSBU? Especially given there will be fans upset their favourite fighters not returning to Smash Bros. or anticipate their return anyway.
Way I see it, SSBU could be Nintendo's Minecraft. They can continue to add to it and it maybe a whole new game in the future (just as how different Minecraft is to 2009 Minecraft) but it will still be the ultimate SSB game.
Option 2. Nintendo vs
(Preferably Sega)
More of an idea for a spin-off than a sequel but could perhaps work both ways. The idea is Sakurai could go back to a standard set of fighters, such as Brawls' roster (bit without Snake) but this game could be cross-promotional with another video game company that have just as much recognisable characters to be made into fighters than themselves. While Namco and Capcom are good choices for crossover fighting games, I believe that Sega would be the ideal choice given both the history and rivalry the two had in the past.
The only problem I see with this option is that such a match-up between Sega and Nintendo would only be of any relevent of interest to Millenials than the current Gen-Zs who are the market today. They don't care about the "90s console war" between Sega and Nintendo, heck it's Sega's own efforts they're still relevent to Gen-Zs without the use of cutting-edge gaming consoles like Nintendo does so only Sega fans might fight option 2 more relevent to their interest than SSBs general fan base.
But in doing Option 2 not only would Sakurai be able to start a new Smash Bros. game that isn't on the shoulders of Ultimate but would be allowed to collaborate with Sega for more fighters to work with. The "contract" in mind would be a fair balance of number of fighters and stages between Nintendo and Sega while Nintendo will still get top-billing in promotional stuff, such as Mario's name before Sonic or final say in what goes into the game over Sega etc.