HURM.
What other series are "set?"
Mario? LoZ? Kirby? Star Fox? Earthbound?
Adding anymore characters to those series would feel a little UNNECESSARY, yeah? Don't really need Junior, Tingle, Krystal, and Masked Man? >:
Definitely don't. I guess it comes down to what terms you consider "set". If by set you mean "This series sold this much, and is this popular, theefore it should have thi many characters" than I would say for sure, Donkey Kong could have two more, and Kid Icarus is really a wait and see.
Now, if you're talking strictly all the important characters, I would say no series (minus Mario, Legend of Zelda, and Kirby) is set.
Donkey Kong: Dixie and King K. Rool
Earthbound: Masked Man/Claus, Porky (Ninten maybe?. . )
F-Zero: Samurai Goroh, Black Shadow
Kid Icarus: Palutena, Medusa
Wario: Mona(Or Ashley?), Captain Syrup
StarFox: Krystal (Andross wouldn't work, sooo.)
ect.
I feel like Tingle, Toad, and Bowser Jr. don't add enough to the storyline to REAAAAAALLLY be needed, but if we had to choose from LoZ and Mario, those are my three bets. Kirby can suck it. We aren't seeing Gooey, so IDGAF about them >:l
At one point Gooey was P2 for a Kirby game. I think he like licked powers? Or something? I don't remember. I read about him, AND LIKED IT.