Here's my problem with all this talk about the Wii U having "secret cores" that aren't "unlocked yet" for use in games: I've been hearing talk about the secret technical power hidden within Nintendo hardware for decades, and it never results in anything noteworthy. The closest we got was on the N64 when Nintendo did a hardware patch with the Expansion Pak, and that resulted in what...a half dozen games that actually took advantage of it (and some of those were worse with the pak, like Konami's Castlevania games)?
Let's say for a moment that the Wii U does SOMEHOW have the power of a PS4 or Xbone inside it, locked away for reasons only known to Iwata: no one will ever make a game on the Wii U that actually uses it, because the damn thing doesn't sell and Nintendo is never interested in making technically impressive games on their consoles. You'll occasionally get your Retro Studios or Monoliths that have more than utter disinterest in showing off console specs, but Nintendo overall just wants to make the same, assembly line cartoony games that look pretty much the same on any console. So unless Nintendo starts selling consoles and starts getting 3rd parties involved, you will never see a game on the Wii U that looks as good as what the PS4 is launching with right now, even if all this talk about Nintendo's "Secret Plan to Fight Irrelevance" is true.
The Wii U has some good-looking games. The Wii U will have some good-looking games in the future because Nintendo is skilled at using strong art to cover-up bad technical specs, but you're only lying to yourself if you actually believe that the Wii U is going to be able to keep up with the next-generation consoles on a technical level.