After Birdo, I think
Diddy Kong,
Petey Piranha, and
Pauline are pretty much guaranteed, but I’m not sure about the other two. Personally, I’m rooting for
Hammer Bro (with Boomerang Bro, Fire Bro, and Ice Bro variants) and
Kamek, since those two were planned to be in previous Mario Kart games but were cut before they eventually became playable in Tour, but I wouldn’t really say either of them are a safe bet, unfortunately. I’d also like to see
Dixie Kong get in (
especially over Funky Kong), though I dunno if they’d make a third of the new characters be Kongs.
My biggest hope, though, is for the last DLC character to be a guest newcomer rather than a returning Mario Kart character—specifically,
Sportsmate from Nintendo Switch Sports, complete with a variety of different body types as variants. Yes, really! Not only do I think they’d fit great in Mario Kart—probably more so than any other potential non-Mario EPD characters—especially alongside the Villagers and Inklings, but it’s the only character that
wouldn’t bother the hell out of me being on the bottom row and to the right of the Mii icon, lol. Of course, I don’t expect it to happen, but I’d be thrilled if it did!
EDIT: Gonna add my latest mockup of my current hopes for DLC characters, of those already in Tour:
I feel like the order on the character select screen works nicely with all of these, too, assuming they’d be released in this order. Birdo is on the top row after all the princesses (well, and Tanooki Mario, lol) and right before Yoshi on the next row; Petey Piranha is right next to his partner from Double Dash!! (King Boo); Pauline is…after the babies and the metal characters, putting her right next to a Peach variant (okay, this one doesn’t have much going for it but the only better place for her would be Birdo’s spot); Hammer Bro is right next to Dry Bowser in the row with all the other Bowser’s Castle associated characters (Bowser, Dry Bones, Bowser Jr.); Kamek comes after all the Koopalings, which is fitting because they’re all Bowser’s highest in command after Bowser himself and Bowser Jr.; and Diddy Kong…gets the unfortunate position of being at the very bottom right after Miis, but hey, of all these characters he’s the most guest-like one since he’s distinctly a Donkey Kong Country character rather than a character born from the Super Mario series (or one that originated before the split like Mario and Donkey Kong themselves), so it works, I guess.
And here’s a bonus mockup with Sportsmates as well: