A few things to touch on (man this thread moves fast!):
1) the “relevancy” argument defeats itself imo. At this point, if we’re freaking talking about Geno, he has remained relevant to an extent because of the fans who were impacted by him in SMRPG. Sora would absolutely be an amazing pick, but that’s not entirely in Sakurai’s hands. It comes down to whose licensing Nintendo can successfully negotiate for and obtain.
2) This will get flak. If there is no Xenoblade newcomer on base roster, then I have a tough time seeing Elma get picked over Rex and Pyra for DLC. Sakurai played XC2 while working on SSBU, and loved the game. Would he pick the lead from the more recent Switch game with a popular character, or the also popular but older game? Time will tell, but I think we’d get Rex and Pyra.
3) Despite Echo Fighters allowing for more characters to get in more easily, people are reeeeeaaaally stretching the definition of “a few more”. In my humble opinion, “a few more” doesn’t mean 8 to 10 echoes on top of newcomers. To me, “a few more” means 4-8 total additional newcomers INCLUDING Echo Fighters.
The man says to “not expect as many newcomers” as previous entries, but we have homies thinking we’re going to get 10 more newcomers? That would MATCH Brawl if i’m not mistaken.
The max I would say would be 15 total, including echoes.
4) Something to consider. Sakurai specifically mentioned the number for music tracks and stages. If there were more to show, I humbly believe that he would not have put the number of 103 as a crowning achievement. They could add more, but i’m not sure they would even have to depending on who the next fighters are.
I’ll expand on this point in another comment in a bit.