Per multiple sources, this project is green lit, has funding and is in final design work, and that those designs are not IPs that are Marvel or Pixar.
However, with any "rumor" as time goes on, things can change.
Not Marvel, Pixar, or presumably Star Wars? That really peaks my interest thinking what it could be.
Can't imagine that it is older IP - nothing from last century that isn't already well represented in parks. I also dismiss the idea of not being IP based. Disney doesn't think that way anymore, and not for that park. I tend to think something with slightly more girl appeal...with Toy Story and Star Wars I am guessing management would worry about "not enough for girls" at the park.
- First thought is Zootopia - a pretty huge hit that is sequel ready - Judy Hopps makes it appeal to girls as well as boys. Family friendly dark ride would be an easy sell.
- A recent yet underrepresented

Perhaps Tangled or Princess & The Frog related. I think P&tF has grown significantly in popularity since original release, and Tangled was a pretty big hit until it was overshadowed by the dreaded F-word. (That's
Frozen in case someone accuses me of cursing. )
- Tinkerbell? That Pixie Hollow section of Fantasyland remains in a design bin just waiting to be built. Not a ride though. I feel like Pixie Hollow's popularity has waned, but don't know if that's just because I have a teen now.
- Wreck-It-Ralph, since a sequel was just announced. Might be hard to pull off to get rights to use characters for a theme park setting. Also less girl-themed than I think they might want to go. I think this and Big Hero Six would be low on the likelyhood scale.
- Indiana Jones ride? Unlikely if it not a thrill ride. However, I still think DHS could use another coaster.
- Final, completely crazy thought - Muppets Great Movie Ride? I think this highly unlikely based on the show being cancelled, but the fact they are building Muppets mini-land? Just maybe...