http://www.gameinformer.com/b/news/...-planned-for-donkey-kong-country-returns.aspx
That was in 2011 mind, so a lot could have changed since then.
If Retro was doing DKCR2 Nintendo wouldnt have pushed out the 3DS version of DKCR, they wouldve just waited and got DKCR2 out this fall and made the money there. I think they are setting up for DKCR2 to come out on 3DS down the line.
Also Nintendo has franchise teams for a reason, Zelda team, Mario team, Mario Kart team, with them needing to get games out why would they put a new team on Mario Kart? That would make no sense.
Why would Nintendo force a full MK game on Retro but let Monolith Soft do what they do best when Retro Studios games have sold better?