Here are my opinions for these characters:
King Dedede: He has the highest chance at entering, because Sakurai created him and many people want him, but he'll probably be a semi-clone or clone of Kirby.
Diddy Kong: Because Donkey Kong is the only Donkey Kong character in there, and Diddy Kong has a special attack of his own: His electric guitar.
Geno: SquareSoft might not let Nintendo use him, but I hear many people want him in.
Ike: He'll either replace Roy, or be added next to him.
Ridley: I doubt he would enter, because he is about as large as Giga Bowser and he flies almost forever, which makes him good for cheaters.
Captain Olimar & Pikmin: I'm not sure if they would enter, because I don't see other good moves that Captain Olimar has besides Pikmin.
Krystal: While Sakurai is removing most clones, I believe he'll replace Falco Lombardi with Krystal, because she is more unique.
Takamaru: Another unique swordsman, but Sakurai might include him, because Sakurai said that he will not add too many Japan-Only characters.
Young Link (Cel-shaded version): As the OOT Adult Link was changed into the TP Adult Link, Sakurai would modify the OOT Young Link into the Cel-Shaded Young Link, because the cel-shaded version is still being used today.
Animal Crossing Male/Female: I doubt he/she/both would enter, would they be fighting with a fishing rod, a bug-catching net, or what?
Claus: He isn't as major as Lucas.
Demiru/Demille: Very unique, but he might either be a trophy or a playable character. Also, Sakurai will not add too many Japan-Only characters.
Isaac: Pretty unique, but will CAMELOT let Nintendo use him?
Jeff: Either Sakurai would add Ninten, Ness, and Lucas, add the MOTHER 2/SNES EarthBound Chosen Four, MOTHER 3/GBA EarthBound characters, or add them as trophies.
Kawasima: He might be the owner of the Hands, but as a playable character, I doubt it.
King K.Rool: Donkey Kong might need a villain, but I hope Sakurai won't add too many characters from one popular title. I'm not saying three is too much, I really mean like 3 characters times the number of popular franchises (Mario, Zelda, Metroid, Donkey Kong, Kirby, Fire Emblem, MOTHER/EarthBound, Pokemon, Star Fox, etc.) wouldn't let them have enough room to add some obscure characters.
Lip: Very unique, but will they let SSBB stay in Japan, switch her with someone else, or just release it outside of Japan? Also, Sakurai doesn't want too many Japan-Only characters.
Lucas: He might be included with Ninten and Ness.
Mega Man: Didn't Sakurai said that he and Nintendo are looking forward to adding him and other 3RD-Party characters?
Oguma: Pretty good, but like what I said about King K. Rool. Again, Sakurai doesn't want to add too many Japan-Only characters.
Ouendan: They are probably not suitable enough to fight (eventhough I submitted and Josh added them), and/or they are owned by iNiS (the people responsible for Gitaroo Man).
AND
Sukapon: Very unique and has appeared in an obscure (and Japan-Only) 2D fighting title. Again, Sakurai doesn't want to add too many Japan-Only characters.