Any PC gamer will tell you that high-end specs and PS4/XBO specs are two different categories. If Ninty doesn't edge out the PS4 in terms of graphics with the NX, there won't be much point for Wii U owners to "upgrade".
Sure, the 3DS-only crowd will be getting some better looking games, most likely, but that does nothing for those of us who really love the beauty of "Mario Kart 8" and would love to see Nintendo play with some different ary styles that require the extra juice.
EDIT: I know that Miyamoto said that all realistic game looks the same, but that doesn't mean that games like Ratchet and Clank haven't benefitted from the extra horsepower of the PS4 - in much the same way that "Mario Sunshine" was a huge leap graphically from the N64.