People who want it to release in 2017 seem to not realize that a 2017 release is pointless:
Nintendo needs to outperform SLIGHTLY the competition, in the end, they just started this generation making HD games, they surely won't start with the NX 2k or even 4k games: The hardware to make a Nintendo console that is more powerful than a PS4, with the same price as a PS4 and to get a good revenue is already out there: PS4 was built with 2012/2013 Hardware, NX will be built with 2015/2016 one...
The stronger power wouldn't affect third party either since most of them either don't know how to make games that look that good because PS4/X1 can't handle them or simply don't support Nintendo...
Waiting for 2017 would make for another major factor: PS4 and X1's install bases would grow A LOT, and I'm shure Nintendo aims to get an NX in the house of those people instead of releasing a new console on a market with a 70M PS4 and a 40/50M X1 ...
