There’s always more that Super Smash Bros can do to push the envelope

“Even if Nintendo wanted to add more stuff to game — and Nintendo likely will do exactly that over the course of Ultimate’s life — we may be getting to the point where more characters or levels would be overwhelming.”

You say that like it could be a bad thing. Super Smash Bros has become a celebration of the history of the game’s medium as a whole as much as it’s about Nintendo’s history. You can never go overboard with it as the medium continues to evolve.

After everything that they've done with smash ultimate, and the fact that they're probably adding even more before release, and possibly even after release, I find it hard to think of them making another Smash Brothers before they have a significantly more powerful system to work with.

I say it is already a miracle that they are able to fit over 28 hours worth of songs into the game on top of everything else, while still adding over a hundred stages and nearly a hundred Fighters.

I just don't see many ways for them to advance the series without something that holds at least twice the amount of data as the cartridges that the switch uses.
I still question how they fit everything onto the current cartridges, as it is.

Maybe a new form of switch will release in 2022 or so, and by that point we might have SD cards and cartridges that are far more affordable and hold far more data than anything currently does.

I have that question for many of Nintendo's first-party games. Super Smash Bros Ultimate, Breath of the Wild, Super Mario Odyssey, and Bayonetta 2 are all games that will be very difficult to improve upon in future installments. I don't think anyone expects their sequels to be as innovative and big in scale as they were, but only time will tell.

Bubble bobble!