Best case scenario:
Dixie Kong
-and-
K. Rool
K. Rool is Kaptain by default. King is his alternate. Wields a blunderbuss.
Both characters are bundled together, along with a stage: Crocodile Isle.
"I am a habitual liar," Sakurai admits, in reference to the "I don't think we can make many more stages" line.
In fact, Crocodile Isle is a traveling stage. Fly from Gangplank Galleon to Crocodile Cauldron, then Krem Quay, Krazy Kremland, Gloomy Gulch, K. Rool's Keep, the Flying Kroc and the Lost World. Each the size of Palutena's Temple. Each with their own Omega form. Each individually selectable. Each with fully orchestrated arrangements composed by Wise, with guest appearances by Kirkhope and Beanland.
A new item is Rambi the Rhino. Squitter can be seen chilling in the back of the Crocodile Cauldron stage. There is a Lanky Kong AT, because why the hell not.
There is a DK Coin hidden in each stage. It does nothing, but it looks cool.
Up, Down, Up, Down, Up, Down, Up, Down as DK, Diddy, Dixie or K. Rool to make Cranky Kong appear in a text box and start berating you about how back in his day, Street Fighter was the closest thing they had to Smash and they didn't even have pits to fall into, and they liked it.