I'm not sure how the licensing works, exactly, but the Warner Bros park in Australia has a land devoted to Oz. It would probably be Wicked, if anything, as it was released through Universal Pictures. The book "The Wonderful Wizard of Oz" is public domain but they would have to be careful not to use any copyrighted material as well.
This is why I still lean towards Zelda, Pokemon, or another domain. Less conflict.