I'm kinda new here, but I these are my hot takes
we are for sure NOT getting a FE rep. Sakuri has almost certainly noted the negative reaction to Corrin (adding Chrom doesn't lock a FE char, he already had a model and they decided to make him an echo for eastern fans). It would be ridiculous to place in another FE char while the pot still boils.
we are probably not getting a Mario rep. The series has been half squeezed to death in terms of smash representation, and while I do understand that it's a moneymaker, there just simply isn't any remaining char (assuming Spirits deconfirm) that would make sense to add, especially as DLC. On a similar note, it's very unlikely that we will be getting any new LOZ chars, for a similar reason.
I considerably doubt mainstream Nintendo characters from already existing franchises will get any representation. This pains me to say as a Louie supporter, but there isn't any char that hasn't been deconfirmed that would make sense as a DLC.
New Nintendo series representation would be cool, but very unlikely. Most top Nintendo series are already in smash in some regard, and most lower Nintendo series potential reps have already been deconfirmed (see: Isaac, Spring Man, etc).
very unlikely we are getting any indie representation, which again pains me to say (Hat Kid supporter), but excluding Steve (whose peculiar movement might be a turn-off for Sakuri) and maybe Reimu (who is a literal who in the west), there isn't any char who has enough support to be noticed.
also, asking for another Square rep is just a waste of time. If square is this stingy with their poster boy, then there's no hope for Erdrick, Sora, etc.
those are my hot takes. maybe they cold takes. idk.