If Dr. Mario was given the same treatment as Lucina (costume first, then decided too different for that), then I can still see Geno, K. Rool, Ridley, and Mewtwo having a chance (as the clones wouldn't have taken as much development time).
Anyway, changing the topic off of that for a moment, what did everyone think of the new Pokemon Fighters announcement? With Hyrule Warriors being a hybrid of two gaming companies with Nintendo characters, and Pokemon Fighters being the same (Tekken and Pokemon), then shouldn't we see another crossover? Maybe Square returning to work on a Mario RPG game...?