March 2015 had a South Korean-only Nintendo Direct on the 19th. April has Xenoblade Chronicles 3D for 3DS coming out in early April while Xenoblade Chronicles X is coming out in Japan only by the end of the month.I suppose we'll see this new Fire Emblem 3DS game released for fall overseas. According to the developer, Xenoblade X's next video will be focusing on the giant mechs. It will likely be presented through as a non-Nintendo Direct like the last couple of videos for the game. Splatoon comes out next in May along with Super Mario Bros version of Puzzles & Dragons.
3DS does have a couple of new games announced for it such as a new Fire Emblem title planned for a summer release in Japan. Strangely, Fire Emblem: Awakening came out first in North America and a month later everywhere else. Nintendo also showed us a brief look at a new Rhythm Heaven title for 3DS, but I don't remember if nay release news info was revealed for it . EAD Tokyo is apparently working on a new Super Mario title, but did not say if its for 3DS or Wii U. We don't know if it is coming out this year.
Wii U's got several titles announced but without releases dates such as Xenoblade X, Devil's Third, Zelda, Mario Maker, Yoshi's Wooly World and Star Fox. Nintendo also teased us late last year about sharing information on Animal Crossing news for Wii U, but its anyone's guess if we'll actually see it come out this year. There's also Fire Emblem X Shin Megami Tensei that Nintendo has not given us an update on since June 2014. Next Level Games and Retro Studios are working on Wii U projects if I'm not mistaken. Next Level Games hasn't released a new title since Luigi's Mansion 2 in 2013 for 3DS, whereas Retro Studios released Donkey Kong Country: Tropical Freeze back in February 2014. Apparently, its new project has been in development since November 2013, but I doubt we'll see it released this year let alone announced at E3. Miyamoto and Iwata did say that there's more new games to be announced for Wii U, so take from what what you will.