I think, like 3D Land before it, this is a deliberately conservative game with a short development cycle so they can bolster the Wii U's lineup quickly. Hell, most of Nintendo's current games fall squarely in that category. And as disappointed as I am, I can't say I blame them. The Wii U needs momentum and it needs it quickly - they can't afford to have their flagship franchises out of action this Christmas season.
Still, this can only be a short-term strategy. If, come next year, they're announcing yet more of these somewhat half-assed sequels, then I think it's going to be a problem. They've already cheapened Mario games from the super-hyped, generation-defining events they once were, and if they keep this up for a few more years I think we'll be looking at them in the same way we look at overplayed franchises like Assassin's Creed or Call of Duty. And that's kind of depressing.