No, XBOne level graphics aren't "good enough for Nintendo". Nintendo is considered the finest game maker on the planet, and in the past their titles like DKC or Zelda:OoT have pushed boundaries of what we thought was possible on a game system. The finest artists should be given the finest tools to work with.
I think XBOne's graphics look lovely. I'ts a great system. But if NX is coming out 3-4 years later, and if it's on store shelves next to a product like XB Scorpio, NX at XBox One levels will seem like a dated product.
Now, if NX is a handheld, XBOne levels would be extremely impressive. But if it's supposed to be competing in the home console space (as well?), it should have more power.
And saying Nintendo won't get third party support would be a defeatist attitude for the company to take. Nintendo staff should be doing anything they can to court third party support. They owe it to their consumers, and they need it if they ever truly want to be leaders again in their industry.
Personally, if I were running Nintendo I'd be targeting something in the ballpark of PS4 Pro, give or take, while working out a deal or two to lure a couple key 3rd party publishers support, if not purchasing them outright. That, in combination with some well executed 1st party titles and a few other unique hardware innovations would get the mass market's attention.
