If this event returns next year, and I certainly hope it does, then I imagine Back to the Future, Wicked, and One Piece would all return (as well as obviously Mario and Potter). Back to the Future could easily be an upgraded version of 1955 or a new makeover with 1985 or 2015. Wicked could get something as simple as the meet & greets (perhaps adding additional ones for characters like Fiyero) or as elaborate as a walk-through with musical elements. One Piece has definitely proven its popularity in Hollywood and could get a heavily modified/shortened version of the Waterworld show. Mario could just do another character takeover and meet & greet with Donkey Kong, Daisy, or Wario. Potter could get... uh, I dunno, a Buckbeak meet and greet? Another projection show? lol
As for new IPs, the past 4D shows at Osaka are a safe place to look: Sailor Moon, Godzilla, and Neon Genesis Evangelion all seem popular enough in the west to justify bringing over. Chainsaw Man would've been my top choice, but that film is so heavily tied to Halloween Horror Nights that I'm not sure it'd work. You could do more meet and greets in the vein of One Piece with Demon Slayer, Spy X Family, or Dragon Ball. The real question is what the walkthrough experiences would be, and if there are any other 80s' or 90s' IPs to balance the more modern anime ones. I doubt Star Trek or Dungeons & Dragons would return, but perhaps they could work with Viacom again and do a Ninja Turtles walk-through/show? If we're sticking in the tabletop or RPG world, then Baldur's Gate, Cyberpunk, and Fallout have potential.
I really do hope this event was successful enough to become a recurring thing. The wait times were never super high, but on my Saturday visit the event was decently crowded; not HHN-levels, but surely enough to make a profit. This same type of event with slightly more budget and capacity would appeal personally to me a bit more than HHN, even, and it's a great oppurtunity to test the waters with new IPs in theme park environments.