I did have one idea... what if the theme is time/time travel? For example, say the long-running rumors are true and some IPs such as Lord of the Rings, Star Trek, and Doctor Who are acquired by Universal. Middle Earth could be an area representing the past, specifically the Middle-Ages/medieval times. Fantastic Beasts could get an area, and could represent the past too, specifically the early 20th century, which is when the films are going to take place. Star Trek would obviously represent the future. And Doctor Who fits with the time/time travel perfectly. Then they would just need to throw in a land with a family appeal (similar to Suess Landing) that still works with that theme. The theming could be even above IOA, with Diagon Alley-esque facades within each world completely isolating them, feeling as if you truly traveled through time and are in these worlds. For example, in the Middle Earth area there is mountains along the side on one side, and on the other side it's buildings in the Fantastic Beasts world, so you can't see the other worlds from either side. Any thoughts on this idea?
EDIT: Also how did I forget Hill Valley? A time/time-travel theme would make for a perfect BTTF park comeback!