The 20+ acre plot in EU more than likely won't be touched until all the lands current expansion pads are filled out which is many many years down the line IMO. Since Wicked would be fast tracked for the parks, the next logical place to do it is IOA as the overall atmosphere of the park jives well with Wicked. As for location I could see LC if Zelda fell through. But In the even Universal keeps LC open for when they do crack the code on Zelda, I wonder if (unpopular opinion incoming) Wicked replaces MSHI?
Playing devil advocate for a second. What reason does Universal have to keep it besides trolling Disney by denying them access to use their most popular cash cow IP their flagship resort that be WDWt