While WoW would have to be stripped down, there are also things that could be added. The keyboard interface in iWork has been customized for those applications. It should be possible to do the same for a game. The keyboard could display images for hotkeys for example. Special servers could be utilized to optimize the experience specifically for the iPad. Gestures could be used extensively.
Most people would probably still greatly prefer to use a desktop or laptop. Still, it could draw some new players in via the app store presence. It could also be superior to existing RPG apps on the iPhone. Warcraft (3), Starcraft, or Diablo would be much easier ports though and probably more successful.