So the leaks killed a lot of my hope for seeing a playable K. Rool in Smash 4.
However, with the way Mario Kart 8 has been handling DLC, plus the Gematsu leak (which I still think holds stock) I think there is a very good chance that we will be seeing character DLC for Smash 4.
And think about it, if they want to actually sell the DLC they will need to include some popular characters. A K. Rool DLC would sell a lot better than, say, a WFT DLC.
It's a pretty dirty approach, but I don't think it's out of the question.