I think the most likely/most logical area to refurb/retheme will be Cloud Cuckoo Land. With the Dungeons coming in 2019, I would really like to the see this part of the park restored and made to look good again. It's going to be getting a lot more visitors in that section of the park so they really need to make that area look vibrant and attractive again like it once was. If Twirling Toadstools made a return; even better imo.
I'm the boy with the bubbles