Well I only know the reason for pikmin Nintendo said It was due to their lack of expirience in HD game design sincce pikmin 3 will be a full 1080P game.
They mentioned that they were not ready for HD development, that they did not know they would need to almost double their work force in order to have these games completed in a reasonable time. So pretty much they were caught off guard. Once games start coming out i think the release dates will start to be smaller and smaller as they get more experience in making HD games.
What... MK8 was never delayed, it was planned to launch in 2014 when it was shown...
That's what I thought.
Just because people wanted the game to be released during a certain time, it doesn't mean that Nintendo delayed the game. Infact, they hadn't even announced anything about when the game was expected, before E3's announcement that it'd be out during Spring 2014.
The only Mario game out in December that I know of, is Super Mario 3D World.