I don't think it will be Metroid. I'd imagine Nintendo wants to give that franchise a break after the "success" of Other M.
I say Zelda because of that cock tease by Miyamoto and the "a project everyone wants us to do" rumour. As well as DKCR sold, I'm not sure a sequel is something everyone wants them to do.
We'll see DKC make a return, though. Maybe as a 3DS game, that would be sweet.
I'm expecting something from the Zelda universe. Probably a spinoff and not a mainline title.
It was already said Retro is not working on Metroid and Zelda.
Do you have a quote?