I'm expecting us to get one retro character (Takamaru being the most obvious candidate) and one historical character (my personal choice being Daitoryo) for sure, but, as for others:
New Franchises (not including retros and historical characters, please keep in mind that most of them are the definition of obscure):
Little Mac (If he counts)
Chibi Robo
Shulk (Xenoblade)
Isaac (Golden Sun)
Starfy
Wars Character (Andy, Sami, etc.)
Primid (No one is asking for him, but he's at least possible)
Saki?
Dillon (Rolling Western)
Zip (FlingSmash)
Mr. Wright (SimCity)
Dr. Kawashima (Brain Age) (unlikely, though)
Nintendog (again, unlikely)
Dr. Lobe (Big Brain Academy) (Dr. Kawashima's more likely than him)
Vince (Art Academy) (If he gets in, I'm going to die of laughter after I die of shock)
Cooking Mama
Existing Franchises:
Tingle (as much as most of us would like to ignore him)
Impa (Legend of Zelda: Skyward Sword)
Ganon (Pig Form) (Legend of Zelda)
Bandana Dee (Kirby)
Robin (Fire Emblem: Awakening)
Anna (Fire Emblem)
Black Shadow (F-Zero)
Blaziken (Pokemon) (He's not obscure, per say, but he's not widely expected)
Deoxys (Pokemon) (Same as Blaziken)
Gigas/Gigue (Mother/Earthbound) (In his physical form)
Am I missing anyone?