Genuinely, what is there to be pessimistic about? They’re arguably the most popular characters from a series that has grown exponentially over the last console era, they’re used by a lot of people and they represent probably the most streamlined stance-change mechanic in the game on a fundamental level. Among a roster of popular new additions from Ultimate, assuming we’re losing a number of third parties, I feel like it would be unproductive to needlessly cut off first parties like this - and you cut a lot of guests. I think your cutting of K. Rool is unnecessary for similar reasons.
Even in the instance that Xenoblade 3 got new content I can’t see Pyra / Mythra being cut. And you aren’t even advocating for that, so frankly I find it very unrealistic that Xenoblade will scale back.
…also man, Ryu is not getting cut. We have three fighting game characters in Smash already, Ryu has been the foundation for this style of moveset design and wiping this whole slate is honestly a bit disrespectful. Not saying Kazuya and Terry need to be back too but surely at least one of them can stay.
Part of the deal is the roster size limit. King K. Rool is never on any of my rosters because I can't fit him in: It's usually a choice between adding him or Mr. Game & Watch or Min Min, or Isabelle or a cut that nobody would seriously entertain.
Pyra/Mythra is two characters, so it's even more difficult to place them when you have to delete two other pretty important additions*. I kinda have been persuaded that they really are pretty important characters to have for Xenoblade Chronicles's cast, so I'll probably try a bit harder on future rosters but...transforming characters really suck in this exercise.
Ryu I actually almost kept, and swapped in Mega Man at the last minute for arbitrary reasons. I'm sure you'll take issue with Ryu and Mega Man being either/or in the first place, but again, I can't add everyone, so some bigger cuts have to happen. It's why the roster also lacks stuff like Robin and Falco.
In the end it's all hypotheticals; rosters are meant to be a discussion starter, and I'm not actually upset or anything (in case my wording makes me come off as such). I do worry a bit about the reaction to the game's actual roster, because I can almost guarantee you it's going to have cuts that everyone beforehand is like "no way are they cutting [X CHARACTER]. Why would you even consider that as an option?"
*in terms of the oddballs, I'm thinking more in terms of some of them should exist rather than that any specific ones should exist.