PS4 is already 3 years old, by the time NX launches that is more than half way, that is also further along than SNES was compared to Sega Genesis. If NX launches and it is LESS powerful or even JUST AS powerful it will fail period. It needs to shoot for a TRUE next gen benchmark that can do stuff PS4 can't and if that means selling at $350 or even $400 if the hardware and games justify it people will buy, Wii U is 4 years old, there is already a market of 4+ million Wii U owners ready to jump ship, that is enough to get a start and if they bring in some of the outliers on the fence then they will be doing fine. They do not need to beat PS4 they just need to be competitive and make a console people want to buy.
One or two "mature" or "hard core" games isn't going to cut it either, Game Cube had that it didn't work then. NX needs to do everything a PS4 does and play Mario, Zelda, DK, Smash Bros, Metroid, etc, and work without any major hitches. It needs to have the same or better version of the media apps, it needs to have a brand new Splatoon fully online with chat and all, ready to go at launch, not a day after.
They also need to get some partnerships going right now, Sega, Atlus, Capcom, Konami, anyone they can bribe, forget the indies they are not going to be the savior that Nintendo thinks. Being the "best" indie machine didn't mean squat for Wii U, it sure as hell won't matter for NX.
And above all else it needs a traditional controller standard, any add-ons or funky controllers either pack-in but completely optional or just sold separately and completely optional.