She's new in relation to the others in her series, not Nintendo's overall history. Out of DK, Diddy, K.Rool and Dixie, Dixie's the newest. Same goes for Rosalina when grouping her with The Bros, Peach and Bowser. Sheik's a bit of an exception thanks to Toon Link, but when lined up with Link, Zelda and Ganondorf she's more on the new side, therefore like the other characters I said relatively new. Not completely new, but somewhat.
Lol, she's the newest... by ONE game.
Honestly, I support both Dixie and K. Rool. I've ALWAYS supported K. Rool over Dixie, and I still do. But ideally, I'd like both, and I don't think Dixie will be completely out. If anything, Dixie probably has a low priority and would be a late character to the game. I do think she'd bring a lot to Smash Bros., though, and with Donkey, Diddy, K. Rool, and Dixie, that completely rounds out the DK cast.
I think DK has more than proven itself to get 4 slots. I can't really see DK ever topping four because if we get these four, that's basically the entire DK main cast. Cranky's charm is being an old crank who yells at the players that he can do better than them.
I've long suspected that Dixie would have a higher chance of making it in before K. Rool because she appeared in the most recent game, Tropical Freeze, until the Smash Direct that is. Now I think K. Rool will get in first, but I won't count Dixie out yet. The past two games at least two franchises got two new characters, the same could happen here. (I could also see Fire Emblem getting four, but it should be noted that FE doesn't sell the best; DK games I think sell way better).
So, yeah, sign me up, just keep in mind that I do want K. Rool first (but Dixie is and always will be my favorite Donkey Kong character).