I think XC:X will fill that void. I'd love it if they made a Zelda game in the same vein as Adventure of Link with the leveling up element.
I agree, though. With Nintendo's whimsical character design, story-telling, and colorful palette, a true action RPG could really breathe some life into the Wii U library.
It'll be awhile before I figure out how to do one of these. :P