I am going to first say that I don't agree with your assessment. Like others have posited the conclusion you are drawing isn't exactly that clear or concise.
They can be working on anything.
Honestly I don't want either game. There. I said it. We don't need another Metroid. Really we don't. Please tell me what new space is being explored in that genre or what hasn't been mined to death? Do you just want a more refined Prime experience? Or a 2d Metroid game? Either way, Tabata, I think I have that name right, explicitly stated that there wasn't another Metroid in development. Obviously he could be lying.
Then let's look at DKC, same question, what more can be done beyond what was in DKCR and TF? Like I feel that Retro has done all they need to do with these games.
So what does that leave? Well there are possibilities of new IP, which it is entirely possible that Nintendo gives them some berth there. Also possible they have made something in another existing IP. A lot of Retro left to form Armature, so I am not entirely sure what kind of game I'd like to see.
However I wouldn't be against an action adventure title or a 3rd person action game ala Bayonetta. Really I am trying to think what kinds of gaps exist in Nintendo's line up and I think they need something akin to Uncharted or sports/racing.
So I guess my answer is that I'd like to see some thing that expands Nintendo's library offering in to an area that hasn't been explored in a while or has never been done by them. I mean why aren't we asking for a Retro developed follow up to Eternal Darkness or something similar?