Not fair for me to rank Grovyle from a series I've never played.
King K. Rool:
95% Chance: At this point, all signs point to go. K. Rool first and foremost, is popular worldwide. Ridley is popular in the West, Takamaru is popular in the East, but K. Rool is popular in both places. This gives him the immediate appeal of an internationally-liked rep. Secondly, Donkey Kong has a rep coming, it only has two characters and DKCR came after Brawl to insane popularity. It outsold its fellow two-rep franchise Metroid about 3-1. Every Donkey Kong Country game tends to be this popular and the series is the most obviously under-appreciated, compared to say, Kirby, or Star Fox. Donkey Kong deserves at least one more rep to bring it into line with these far less popular and relevant series. There is a hundred-percent-chance it gets at least one new rep.
Who could possibly take that place? Well, the series already has two protagonists. Surely it needs a villain. Every series that gets a third rep follows this trend: Mario, Star Fox, Kirby, Pokemon (until they removed Mewtwo to great resentment). If Sakurai were to buck a trend like that, we'd need a good reason for it. Dixie Kong is not a good reason. You can argue she's a good rep for the series or that you like her as a character, but she is extremely similar to Diddy Kong, besides her hair and the fact she's a girl. She has very few discriminating features that make her unique. In a game where every newcomer so far has emphasized uniqueness, no one in the game bears a resemblance to King K. Rool. Let alone in his own series.
You see, where Donkey Kong is a brute and Diddy Kong is a weasel-y little prankster using improvised inventions, K. Rool is a kunning and kruel villain. His potential knows no bounds, he can do almost anything you can imagine. And all of it was in a side scrolling platformer where it can be directly translated into a Smash Bros game. Sakurai can if he wants just steal all of the moves K. Rool ever did in DKC1-3 and he has a unique, fun moveset. But he obviously won't do that, he'll just take all those moves and whittle them down to the point that he has a greatly defined set that establishes a new heavyweight archetype in Smash Bros. K. Rool is the only potential newcomer in that archetype who can up the ante after Bowser, then Dedede. Ridley is simply not comparable in this respect.
He completes the trouble king match-up. It gives a new character who is deafeningly shouting out that he is an antagonist. The body shape of a fat king with a cape and crocodile features is completely original. He represents Rare and all their games which had similar characters. There are just so many good reasons he should be added to coincide with Sakurai's vision for Smash Bros. He should be top of the list, alongside Mewtwo and Ridley. If he isn't added it's going to be total bull and I'll be so disappointed.
100% Want: One of the characters I most want and have ever wanted. I remember when Brawl came out and the K. Rool support thread was like a funeral, it was so depressing, but everyone knew his time would come in the next game, because it just had to, it's only fair. He's the best character as of yet unused in these games by Nintendo and he represents so many different things to so many different fans. He's the classic showboating, egotist that is lacking in Smash Bros. His moveset would so easily be fantastic and is smooth to transition into a fighting game, as all he does is fight. Compare that to even Donkey Kong and Diddy, who mostly platform, he is actually a better fighting game candidate than they are, and the same goes for his competition.
K. Rool is also just an awesome character. He's funny, original and full of surprises. He's the kind of villain who is never the same and never fell back on repeating the same idiotic pattern like Bowser or King Dedede, which made him the antagonist of the Country games on SNES. Yes, without K. Rool there wouldn't be any Country games. Donkey Kong was just a license, what made the games shine was the setting, the atmosphere and the enemies. K. Rool and the Kremlings is what gave colour to the world of Donkey Kong Country. Without K. Rool, Donkey Kong would still be fighting Mario.
I could gush over how cool the character is, but it's also his fans I greatly respect. They're fans who have stuck by the character despite being snubbed for a decade, because he represents something very precious in their childhood that they want to return to modern games. A character who is more than just a bunch of mechanics thrown together to make a seamless boss fight, a real personality who brings his own depth. K. Rool represents the time in gaming when everything was given a special focus to create the very best experience possible. Fans of K. Rool, fans of the original DKC trilogy and fans of that great, withered developer Rare will all be satisfied by his inclusion, and I'd love to look into the K. Rool support thread if he was revealed to see the culmination of years of hoping and praying for his inclusion. That joy is the essence of what we all love about Smash Bros. Lets see it happen, Sakurai!
Louie Prediction: 8.5%
Not a bulborb, but any Pikmin newcomer is fairly unlikely considering how they'd necessitate being a clone fairly heavily.
Takamaru Prediction: 45%
These tend to go up over down if there have been no new developments.
E. Gadd x5