I think they COULD do a reveal trailer for another new character. I mean, if they are planning DLC, why break the trend now? Then again, they could also just do Mewtwo and nothing else.
Either way, I disagree with wanting K. Rool in DKC3 before anything else. DKC3 is likely years away; I'd far rather get K. Rool in ANYTHING ASAP, honestly. Just to show as soon as possible that they still want to bring K. Rool back. If it means bringing K. Rool back into the spotlight through a variety of DK (and maybe Mario) spinoff games, sure, I'll gladly take it.
DKR2 is probably the best bet, though, and if it is legit, its one of the top new games that could get revealed.