This got kind of buried in the Wii U Controller Iwata Asks thread. It seems we now have a more solid release window for Pikmin 3.
Note: The astronomical spring (Northern Hemisphere) begins Wednesday, March 20, 2013, and ends Thursday, June 20, 2013.
I don't know if Nintendo is using the astronomical definition.
Source: http://iwataasks.nintendo.com/interviews/#/wiiu/gamepad/0/2Iwata Asks said:Yamashita
For example, something with a lot of small characters appearing like Pikmin([see note] 20) was surprisingly all right.
20. Pikmin: The first game in the Pikmin series, released for the Nintendo GameCube system in October 2001. Pikmin 3 is scheduled for release for the Wii U console in the spring of 2013.
Note: The astronomical spring (Northern Hemisphere) begins Wednesday, March 20, 2013, and ends Thursday, June 20, 2013.
I don't know if Nintendo is using the astronomical definition.