General list of what Nintendo devs and some of its dev partners have released or preparing to release:
Monolith Soft - Finishing up Xenoblade X for Japan release, localization underway
Retro Studios - Assumed to be working on a Wii U title, development began in late 2014
Development began in late summer/early fall 2013
EAD group # 1 - Released Mario Kart 8 last year
EAD group # 2 - Finishing development on Splatoon
EAD group # 3- Working on Zelda Wii U , project delayed
EAD group # 4 - Finishing development on Mario Maker
EAD group # 5 - Star Fox, co-development with unspecified outside developer
SPG # 5 - Released Steel Diver: Sub Wars last year (co-developed)
EAD Tokyo group # 1 + Grezzo - Released Majora's Mask 3D (co-developed)
I guess they've been working on something else for quite some time considering how long ago MM3D was finished
EAD Tokyo group # 2 - Released Captain Toad last year, currently developing new Super Mario title ... apparently not for Wii U according to Miyamoto
Intelligent Systems - Released Code name Steam, finishing new Fire Emblem 3DS summer release in Japan, apparently co-developing Fire Emblem X SMT with Atlus
ND Cube - Just finished Mario Party 10
Good-Feel - Finishing up development on Yoshi's Wooly World
This one's finished and just waiting for a release / bug-fixing ... someone from Germany whispered to me
Camelot - Released Mario Golf: World Tour last year
Hal Lab - Released Kirby's Rainbow Curse, Triple Deluxe last year
NST - Released Mario vs. DK: Tipping Stars this year
Do they still have multiple teams or is it only Mario vs DK nowadays?
1-Up Studios ( originally Brownie Brown) - Co-developed Mario 3D World & Capt Toad
Game Freak - Released Pokemon Ruby & Sapphire remakes last year
Working on a not-on-Nintendo platforms multiplatform game for Sega
Monster Games - Finished Xenoblade Chronicles 3D port
Next Level Games - Apparently working on a Wii U title
Arzest - Released New Yoshi's Island last year
Hopefully not working on a game for Nintendo again
Alpha Dream - Released Mario & Luigi: Dream Team in 2013
Bandai Namco - Unconfirmed, but may do console port of Pokken Tournament Wii U, released Super Smash Bros last year
Hopefully they don't work on Starfox again, They ruined that series already
Masahiro Sakurai (freelance director)- Released Super Smash Bros last year
Genius Sonority - Released Pokemon Shuffle this year
Koie Tecmo - Released Hyrule Warriors & Fatal Frame 5 (Jpn only) last year
Valhalla Games - finishing development on Devil's Third