Wii U has already damaged Nintendo's home console business more than the GC. It's even given people reason to think that Wii was just a fluke.
Nintendo could support the Wii U and replace 3DS this year, but for what? What would they gain with barely supporting the machine for 2 years? To become even more irrelevante in the home console business?
If they want Nintendo like profits they won't get them id they keep supporting a soon to be dead console. They really need a new one.
NX could very well be a name for na ecosystem that shares two consoles: a Handheld and a Home Console; It could very well be not one, but two devices. And if rumours/patents are to be believed, it will be both.
Why shouldn't people consider it more powerful than PS4? What Nintendo console wasn't more powerful than the best console in the previous generation? Even if by a smaller difference.
People say it will come out this year because it's more than obvious that of both consoles, Wii U has the least fighting chance of lasting another 2 years on the market.
It isn't just a case of "i wish it is, therefore it is", it's more about looking at what's in front of you: 3DS is in a better shape than Wii U; has more support; more appeal; it hasn't direct competition from other handhelds.
Wii U is exactly the opposite: no appeal, no support, 2 dominating competitors.
Should Nintendo risk releasing a new home console in 2017 for the competition to out do them in 2018 and have a Wii U scenario all over again?