I'm just going to copy/paste what I wrote over on another duplicate thread:
I knew there would be five more characters yet to be revealed. Part of me wonders if it's just for DLC, or if they characters are still in-game, waiting to be unlocked (I hope it's the latter, and also that we might still get some DLC).
As for who they might be, well, there WAS that rumor that the final characters are Ridley, Mewtwo, Mach Rider, Dixie Kong, and Impa. As far as those choices are concerned, I'd feel satisfied... but then there's be no Rhythm Heaven character. I'm not big on the Chorus Men/Choir Boys specifically, but I want some form of Rhythm Heaven character to be playable, particularly Marshel, since his design is basic enough to incoporate a variety of different Rhythm Heaven games, as opposed to a character who's specifically known for one thing (that being singing).
As to who of the five previously mentioned characters I'd remove in favor of a Rhythm Heaven character... Gosh, this is hard. I'd like to see Dixie Kong, since I want a little more DK representation, but I'd also like Impa because I feel like The Legend of Zelda deserves at least one more newcomer this time around. The Mach Rider is a unique choice, plus Sakurai's favorite (if I recall correctly, though I don't know where I read it), and Ridley and Mewtwo don't really need a reason behind them at this point...
...Honestly, I'd got with Dixie Kong, not that I don't want her, but I find her the most expendable of the five, plus next time, where she'd be paired with King K. Rool, would be a perfect time to introduce her to the series!
...So yeah, I'm going to guess Ridley, Mewtwo, Rhythm Heaven character(Chorus Men, Marshal, whatever), Mach Rider, and Impa.