Discussing the roster size this time around just makes it feel like all of our expectations hinge solely on how many characters return, and honestly that feels detrimental to the individual identity of the next smash.
It's as if we kinda now expect the next smash to invalidate the previous one, like it's a longer-term version of a yearly sports game or so. Granted, Nintendo and the Smash Team is partially to blame for this- you can't buy previous entries that aren't Smash 64 anymore, and unlike most fighters Nintendo really won't let this back-catalog even get played at big tournaments. There's other factors like how Brawl just really isn't gucci competitively but even then, 4's identity at this point has become "the crucial parts were done twice as much in Ultimate- but there is a City Trial-like mode on the version that wasn't even used for tournaments after the console one came out".
And I suppose that's the reality of a crossover fighter going Everyone Is Here- now every previous game doesn't have unique "you can only play this character in this" aspects going for them, they're now a subset of Ultimate. Add on to how 3rd-party characters are treated less like guests and more like part of the family (see: banjo's trailer) and it leads to a lot of balls to juggle.
I think Marvel vs Capcom handles it really well in terms of roster identity at least- it seemed insane to leave Mega Man out of 3 and Tsukinoko vs Capcom but it allowed the focus to be put on Tron Bonne, Zero, and Roll respectively despite those limited resources. And honestly, in a fighting game era where characters over functions philosophy has led to both bison and heihachi returning from the dead to their respective series.... I'm strongly prefering new and weird choices over just playing the hits again ad infinitum. So if a "BWD over Meta Knight" situation presented itself in the next game... honestly, that's just fine considering we just got Meta Knight in Ult. Maybe the next game can be different enough in gameplay that I'd be wishing to see those who didn't make the cut in that fidelity, but as it stands the abscence and additions will go a long way towards giving not just the new game an identity of it's own, but Ultimate a retrospective identity to it's roster that isn't just "Yep it was all of them at the time- but Smash SUPER Ultimate 2 did all of that and more so it's in the same lot as 4 in that regard".
ninja edit:
though i don't think the roster will be anything less than 60-65 before dlc. If Bamco does anything with their rosters it's certainly quantity- asset reuse or no, there's an insane amount of characters in the new Dragon Ball Sparking Zero game.
double ninja edit:
i also forgot that mega man was skipped in SVC Chaos for the Mega Man Zero incarnation of Zero. Regardless of the quality of the gameplay you gotta admit that was awesome.