There's a lot of posts in this thread that boil down to, "Oh no, it's not X86, that means it's going to suck!" What exactly is so inherently good/modern/powerful about x86?
Let's not forget, only in this most recent generation did the leading console manufacturers switch to x86. The Xbox 360 used PowerPC, just like the Wii U. I suppose that x86 could in theory make games easier to port, but even that is somewhat questionable—I don't think we're getting more or better PC ports this gen then we did last gen, for instance.
If I had to pick the architecture I thought Nintendo was mostly like to choose for NX, I'd go with PowerPC. There's nothing inherently wrong with PowerPC, and Nintendo doesn't like change. Not saying it will happen, but I think it's as likely as ARM.