On what basis? Smash has always been very conservative with cuts (as per stated by sakurai on how much he dislikes removing characters without good reason), and it only falls down to a couple of reasons -
1. 3rd party issues. Snake was hit in smash 4
2. system limitations with the 3ds. ICs were cut and Pokemon trainer was gutted because of that
3. Production time limitations and priorities - it prevented Wolf/Pichu/young link/roy from returning in brawl and then Lucas in smash 4.
Unless nintendo loses their mind and downgrades from the switch for no good reason, point 2 is bust. And the thing about 3 is that they took a risk and brought everyone back. They ended up selling 30 million copies and now you're arguing that they're going to cut stuff for the sake of doing so?? Is it worth cutting one-third of the roster so that we get brand new graphics??? Especially when those cuts happened to clones, none of which were actual unique characters.
You're invoking precedent. Ok, so, in terms of precedent, every Smash game has rebuilt its roster from a much more ground level, effectively (not 100%, but mostly) starting over development-wise. Ultimate was the only one that didn't. So based on precedent, Ultimate would be an outlier. Maybe we get some deluxe port, but I'm not going to proceed as if that's a foregone conclusion. That's even more unprecedented for Smash. Even if we did, eventually the roster will have to start anew, this method isn't tenable. Sakurai has said as much.
It's also Nintendo's MO to more often rebuild sequels than just take the package and keep going. It happens, but it's not the norm. Not that I'm saying they don't use any prior asset or base, just rarely in the same vein as the 4 to Ultimate progression.
And when the roster does rebuild, there will be cuts. A bunch. Because reaching the current count from an incipient stage isn't feasible. Previous games were conservative with cuts because up until 4 they had the resources to bring most of the roster back if they started again. Now the roster is basically 90, and with newcomers on top of that, there simply won't be the time/budget. So cuts will have to happen to a greater extent.
They ended up selling 30 million copies and now you're arguing that they're going to cut stuff for the sake of doing so??
It's not cuts for the sake of cuts, it's cuts because making the roster again without cuts isn't feasible, and building on the current roster indefinitely isn't realistic. You can't attain that quantity with the time/resources Smash is granted.
And yeah, Ultimate has sold 30 million copies. Despite that, Sakurai has still already on multiple occasions warned not to expect something like it again. Take it up with him. With the most recognizable faces from Nintendo, retaining a strong handful of the third-parties, a compelling selection of newcomers, any other vets you have the resources bring back, and a successful system/large install base, the next Smash will still do very well.
It's also really funny how you forgot that for the 3rd reason - the "cuts" came from Mother/Pokemon/Zelda/FE in brawl and then star fox. And the hilarious thing is that roy was literally worked on for brawl (in the datamined content) and then returned asap in smash 4 dlc. So tell me why FE keeps being brought up all the time. Shall we talk about Pokemon given Pichu and jiggs (almost cut in brawl) precarious position? Or how squirtle and ivysaur were just removed completely instead of being separated? The former isn't really a great point given how its moreso of a 2nd reason, but since we're on that subject it shows nintendo and sakurai's priorities in these ~cut talks~.
I didn't forget, the current conversation was also about FE/swordsmen. When the roster rebuilds I do think we'll lose characters in Mario, Pokemon and Zelda as well, because the more characters you have, the more likely cuts are. At least with the first-parties. But I'm not convinced we'll both lose a unique character and get a swordie in those series, which is the part of your quote I was replying to. I do think that's likely with FE.
Go ahead and talk about Pokemon, if you want. It's gonna get cuts too.