This is totally out of left field. But...
Considering that Universal tried it before in Japan...
...the fact that Universal owns the rights to Wicked...
...the fact that Disney no longer has ties with the property...
...and the fact that Universal seems to have excellent ties with Warner Brothers in the US (Harry Potter, Scooby Doo, The Shining) and seeing that it more than likely won't go to Six Flags due to brand integrity...
Wouldn't a re-theme of Berk to Oz make a LOT of sense, or even as an addition on the expansion pad?
Flying Attraction (No brainer. Make it Glinda's Bubbles, or a Hot Air Balloon, or a flight on a broomstick from the Wicked Witch's castle. Or even Dorothy's house, if properly placed.)
Splash Battle (This could be a boat ride through the swamps of the Forest, or be transformed into a Fantasyland-style Dark Ride, or any number of attractions.)
Heavily-Themed Coaster (Themed, again, to one of the flying apparatus in the film, or even something original, like... say, Tin Man's Amazing Invention. A Scarecrow CropDuster. I dunno. It wouldn't be so difficult.)
Emerald City Theater, hosting a show that can definitively destroy every show currently on Disney property, a 1 hour and a half version of Wicked, complete with concessions, a Oztastic Beauty Boutique to get made over as Dorothy did, a merch store where they will make thousands of dollars a day...
Plus, this could truly be the Pandora of Universal, with Munchkinland's luminescent flowers, the creepy HHN-style Forest, and the Emerald City itself glowing and sparkling. The scenery is arguably just as breathtaking as Berk, and as there are few overhead shots in the movie, the terrain itself can have a lot of creative liberty.
The instagrams of giant lollipops and munchkin sweets, walking down the iconic Yellow Brick Road spiral, and the photos of millennial friend groups facing the emerald city, arms linked, would be instantly recognizable and rival even the best photos in Diagon Alley.
Not to say that Berk would be bad, but... if Uni wants to stick it to Disney by building a park where each land has a castle... this would be the bet. If Uni wants a beloved IP that has stuck with us like Snow White and Mickey Mouse, this would be the Princess-killer.
EDIT: Universal has come very far since 2011, and by utilizing the seminal Warner Brothers property they could go all in on the wish-fulfillment of the land and not be forced into creating off-brand lookalikes and flat-looking buildings, instead creating a truly realized land.
Universal Studio Japan Land of OZ