Some quick thoughts on a hypothetical Rhythm Heaven character...
The conversation often comes up about which characters appear most frequently in the series. I don't think this is the right way to choose a Rhythm Heaven character and, evidently, Sakurai doesn't either. If we were gonna get Chorus Kids, it was because that idea was unique and compelling in its own right and not simply because they're the face of the series. Who is the face of RH is a loaded, difficult question... it's why we haven't landed on one catch-all choice for a "rep" in Smash. Nobody stands high and mighty above everyone else as the defacto mascot, main character or however else you'd like to judge this sort of thing.
I stand by the fact that Chorus Kids are an ingenious choice. Many if not most Rhythm Heaven games involve teams of characters, and a Rhythm Heaven character would probably have some kind of timed input mechanic, so there you go. A trio of characters who need to perform actions in unison, or in sequence, they'd emphasize this as clearly as possible. Thematically, RH is all about music. So here are three characters who perform music. They're also representative of a recurring 'race' of characters within the series, one shared by Play-Yan and Marshall. And being relative blank slates, they wouldn't look out of place pulling out everything and the kitchen sink. On a surface level they appear to be a weird choice, but surveying closer it really all makes sense.
So do I think they'll make it this time? Simply put... no. For starters, I'm not sure how much this amplifies the odds of a new Rhythm Heaven character to begin with. If this is releasing in 2026, and appears to be in relatively early development, it hinges greatly on when Sakurai began crafting the roster and if there was any word of this game internally at the time. Not that he couldn't have landed on a RH character without it, but I think the improved series relevance would substantially benefit its case. If this DID land within bounds, I think we'd finally get something. As is we'll have to see.
If we get a character at all, I still don't think they would be Chorus Kids (as things stand). Even though they remain my most wanted choice, it feels as if that ship has sailed. Frankly, back during Smash 4 we had already gotten RH Fever without the Kids in tow. So perhaps this sort of thing doesn't matter that much anymore, but Rhythm Heaven DS / Gold was maybe 3-4 years old when the Smash 4 roster was being decided and is about... 17-18 now. That's a big difference and I'm not sure the Chorus Kids would be at the very front of this conversation anymore, at least the way they would have been as the mascots of a game still freshly in mind. Then... who WOULD it be? I have no idea! I really, truly have no idea.
Karate Joe? I think he's kind of the greatest fallacy involved with this thirst for a 'main character' figure. Yes, Karate Joe always has a role in a new RH game. That's a privilege only shared by a number of other characters, notably some variation of Yuka / the Rhythm girl and the Barista. And I suppose the Monkeys? Out of these choices I find Joe the least compelling by far. I like him as a character, but not as a 'representative'. In this world of colorful wacky roles and scenarios I think a martial artist is a pretty uninspired way to show what the series has to offer. And I would find it a bit jarring to see him as a 'prop' character, unless he is something of a summoner or incorporates a Chorus Kid / Monkey partner on his shoulder as some concepts suggest. But on his own, I don't think he's a good choice. The other two? IMO, good choices, but I wonder if they lack a certain core identity or x-factor that was possessed by a concept like Chorus Kids. And would they want to revisit the team mechanic?
Bottom line, I am still not getting my hopes too high for Rhythm Heaven on the (base?) roster, but I hope the fact that the series is not dead and buried is enough to continue to keep it on the radar, to let it be more of a frequent discussion here, and maybe to see some more sufficient nonplayable content like an Assist Trophy, new songs or even a stage. In the meantime I'll continue to meditate on what character I think is appropriate for RH in the current day, putting my bias for the tried and true Chorus Kids aside. One thing is certain though, things look much better for Rhythm Heaven right now than they have in about a decade. So I'll bask in that for a little while.