Well, first of all I would have to be willing to buy a WiiU in the first place, and right now there is no draw for me, no title making it worthy. OoT3D was a bit different because it was the chance to play my favorite Zelda game on a handheld, thereby being able to take it with me anywhere I wanted to go, and yes, the upgrade of graphics, gameplay, etc. featured in, it was that particular thing that really made me willing to shell out that amount for it. I could still play OoT on both my remaining Nintendo consoles without a problem, but the handheld aspect just was that more appealing to me. Also I didn't already own any handheld device, so I wasn't replacing anything.
But the thing is, I already have a Wii, I have the Wii that is still backwards compatible, allowing me to play GameCube titles like WW on it. The WiiU does not offer that, which makes me reluctant to upgrading, not without there being a significant game title drawing me to the system. Do I want WWHD? Of course I do, I adore the graphics upgrade, but better graphics is just not enough for me to want to replace the system I already have when it means losing things my current system is offering today. How much will I be willing for the game itself? Not sure, to be honest. But first I would need to actually be willing to buy the system it's on, and right now, I'm not.