K Rool is one of the most requested characters worldwide, and the only true villain in the DKC series. Even his trophies in Melee and Brawl addressed his massive popularity.
He wasn't in the last two games, but other than that, hes a prime choice for a DK rep. He might make an appearance in the next DKC game (considering Retro didn't want to ride the coattails of what RARE did with DKC and K Rool, they wanted to do their own thing. Now that they have proved they can make great games, not that they needed to, I could see them using K Rool again, maybe.)