I think that it could be amazing. I'm not saying that it would be amazing, but it could be. Final Fantasy was a medieval fantasy series, but started shifting to the use of more futuristic elements around Final Fantasy VI. VII was heavily steampunk in style, and the latest games are even cyberpunk! The games are all generally well-received, though. Nobody says "Final Fantasy XIII is a bad game because it was a cyberpunk setting when the series roots are in medieval fantasy." Not at all. They say that it's a bad game because it's incredibly linear and does away with many staples of the series. No Zelda game is going to go full-out steampunk in the aesthetic sense, but I could easily see a game using many steampunk elements. After all, look at what the series has done already. Steamboats, steam engines, Great Bay Temple, Lanayru Mining Facility, the beetle, the hookshot, the clockwork architecture in Clock Town, the robots in Skyward Sword and Goht--a robotic bull--in Majora's Mask. The genre is incredibly flexible and if done right, a shift towards the use of more steampunk elements could breathe fresh air into such a formulaic series. As long as the series sticks to its roots in terms of gameplay and tone, it could easily be done.