HD development has been tough for Nintendo

imagine how mad people are going to be when NX is "held back until 2017. ;)

I think Nintendo has been gradually getting worse with this date thing.

I had a hunch that Star Fix Zero would get delayed though.

It has always been like this, or at least since the days of Nintendo 64. Nintendo's agenda has always been to try to release games when they are ready, rather than trying to meet deadlines. That's one of the reasons we see so many Nintendo developed games among the top 100 best games.
I prefer delayed games if they become better because of the delay.
In some rare cases Nintendo has postponed their releases to avoid draught. I believe Donkey Kong Tropical Freeze was such move.

3 reasons I see Nintendo delaying this game

1. Marketing budget. This is the most packed holiday Nintendo has had in a long while. They of course want to keep pushing the likes of Mario Maker, Splatoon, MK8, and Smash as well as new releases like Xenoblade, Yoshi, Mario Tennis and AC: Amiibo Crossing
2. Whiners. My god... people kept WHINING about Star Fox Zero so much. So they're delaying it to improve the textures a little more and refine the motion controls role in the gameplay while making standard controls more easy to snap into.
3. Nintendo has to extend the life and relevancy of WiiU

Yes nintendo does have a tendency to do that, but other companies do that aswell.

Yeah, Nintendo has a habit of delaying their games as of late. Wasn't XCX originally supposed to come out in late 2013?

If you're looking for more games per company, Sonic Boom Fire and Ice for Sega, Ratchet & Clank for Sony*, The Last Guardian for Sony (we're on delay number six or so now), didn't The Order have a release window of winter 2014 at one point before it got pushed back?, et alia.

I've got nothing for Konami because MGSV is pretty much their last game for the forseeable future. And The Witcher is CD Projekt's only game as well, but even Sega, a company with a handful of non-Atlus games this year, delayed multiple games. Nintendo's been pretty bad at it this gen but they're just catching up to a trend established last gen by the rest of gaming. Sort of like how they're just catching up to HD now; and those two statements go hand in hand for a reason. I'd like to believe that they're about caught up with that and that the next console won't have this issue nearly as much, especially since about half of the delays we've seen for the Wii U are to stagger out releases year-round since only Nintendo releases games for it. You'd assume with a unified platform that won't be a problem since we're then getting anywhere from 1.5 to two times as many games, third parties notwithstanding.

*Yes, technically R&C didn't have a release date as a game but it was expected to launch near the movie and when the movie was delayed, Insomniac even came out and said "the game's pretty much done and could've released this year." 

Sure, but there were a lot of features in the August update that were mentioned before release and not included on disk.  I would bet that even the items on disk were modified before release.  I don't usually like this method (reminds me of the recent Sim City), but I think Nintendo has handled it fairly well.  I wouldn't mind a polished Star Fox with the promise of extra content in the future, especially if Nintendo keeps communication about the updates like in Splatoon.

People was whining that Wii U have to has a 5 year life cycle.
Nintendo decided to delay games in order to fill those 5 years, but only with the announced titles because they are not going to keep wasting money on that console.

NX is the future.