Ahh I get that feeling, most of my remaining most wanted got deconfirmed during the base and DLC cycles. At the bright side we did get Kazuya despite the Heihachi mii, so there's a silver lining at least. Who do you want that's still not deconfirmed btw?
Doomguy's my big one; him, Geno, and Dante were in my top three, in no particular order. Interviews seem to indicate that he's not happening, though.
Amaterasu from Okami would be great, but considering that Resident Evil, Monster Hunter, and Devil May Cry didn't make it into the playable roster, I don't see Okami making it.
Likewise, 2B from Nier Automata would be amazing, but I doubt that's going to happen. (mostly because I don't think they'd want to end off with a combo-heavy character like what happened in Smash 4)
Captain Toad, Bandanna Waddle Dee, Dixie Kong, or any Zelda character (it's been twenty years since a new unique one was added - I'll take Tingle at this point) would be great, but I don't see any of them being the final DLC character given how the past DLC characters have gone. (first party characters either seem to be veterans or promoting something very recent, with Piranha Plant being the sole exception - even then, Piranha Plant seems like it was intended for the base game, since it's the only DLC character with a Palutena's Guidance)
Beyond that, I'm not sure - Crash Bandicoot, Master Chief, Ryu Hayabusa, or Sol Badguy would be great, but I'm not up to date on those series, so I'd mainly want them in from a historical standpoint, as opposed to being a super-fan of any of those series.
(I'm assuming that a character being a Mii costume, assist trophy, or post-release spirit rules them out)