Retro Studios head explains their reasoning directly
Remember when I said Reggie would be watching you on social media? Well it turns out he wasn't joking, as he sat down with Retro Studios' Michael Kelbaugh to ask the question many people were thinking: "why is there going to be another Donkey Kong game so soon?"
It turns out that I was correct in that the "unfinished business" partially involved content cut or divined during the creation of Donkey Kong Country Returns, and that the studio wants to revisit that one more time. That's completely fair. While I would had loved a new Metroid game announcement, a solid sequel to one of my favorite Nintendo games in recent memory would be great as well.