Assuming we only get one DK newcomer, I basically see it this way:
If Sakurai saw specific demand for K. Rool, and he saw potential he wanted to work with, he would've added K. Rool. I believe Sakurai has a lot more control over character inclusions than it might seem at first. If he really wants to include K. Rool specifically, then he will.
If, however, Sakurai saw a more general demand for a "DK newcomer" in general, or didn't find K. Rool particularly compelling, he might have sought out a suggestion from the DK IP team/Nintendo. In that case, I highly doubt they would even bring up K. Rool as a possibility. They'd want to push the more recent games, with characters that they are willing to promote. In that case, we'd most likely just end up with Dixie or possibly Funky.
I have my doubts we'd get both K. Rool and Dixie. Yeah, we've gotten more than one newcomer from the same series at the same time before, but we're supposed to be expecting less newcomers this time, and honestly, when has the DK series ever been given generous treatment in Smash? This is assuming we even get one character, too. I think there's a less likely but still very possible chance we get nobody. I think the main condition on which any of these characters get added is contingent on Sakurai's own interest in pursuing them, and I'm not quite sure I believe he has that interest. I'm really just hoping that K. Rool's ballot performance did enough to persuade him, because without that as a factor, I doubt Sakurai would willingly pursue a DK newcomer. He just doesn't really seem to care much for the series.
Hope I'm completely wrong with all this, though, and we end up getting K. Rool, Dixie, and a ton of new content from the series.