If Nintendo made a Zelda RPG, I would buy it. Not because I would be terribly excited (I would probably be pretty angry), but because I know that Nintendo would probably make it better than any other company. I believe Miyamoto has stated that he does not like RPGs, but if they somehow got him to work on one he would probably strike a nice balance between adventure and traditional RPG elements.
If Square-Enix or Capcom made it, I would hold off on a purchase.