This is the definition of a 'non-story' but as an unashamed Retro Studios fanboy, I often find it hard to contain my excitement. Retro Studios hasn't yet announced what it's currently working on for Nintendo -- but they will. Very soon, according to Nintendo's Hiro Yamada.
When asked about Retro's absence from the development of the Donkey Kong Country Returns port for the 3DS, Yamada said the following...
“We wanted to use Retro’s development resource for another new title, so we talked to Monster Games about porting this title."
Retro Studios did a bit of work on Mario Kart 7 for the 3DS but its last major title was Donkey Kong Returns. I'd argue that game was the best 2D platformer of last generation, particularly in terms of level design. Then there was the Metroid Prime series. You all know how I feel about Metroid Prime -- it's one of favourite games ever made.
It's all a bit obvious -- of course Retro Studios is working on something, but it's good to be reminded of that fact and it's good to hear that some sort of announcement is on the horizon. Whether it's a reboot of a known franchise, another Metroid game -- whatever. I expect to play and love whatever these guys put out. Just hurry up and tell us what that thing is!