WDW needs a big response. Parks and Experiences is still doing fairly good with all things considered so I have some optimism. Especially with so little spending for the 50th. With the removal of free fast passes, termination of the Magical Express and price hikes, they definitely need some good news for fans. Plus, like said earlier, Chapek needs to deliver 'big news' to strengthen his leadership appeal or he may be facing a swift departure. Below is what I believe are realistic announcements that could be introduced at D23 as they relate to just the US Parks.
EPCOT: More info about the re-Imagineering of the park. Hopefully some news on Play Pavilion and the Festival Center. I think there is a good chance we see one more surprise project since the crews are already on site. Could be one already announced and now green-lit again (Spaceship or Mary Poppins), or something new like Figment overhaul or Encanto.
Magic Kingdom: Do we finally see a Lilo and Stitch replacement or Speedway switchover to Electric Cars? My hunch is that Wreck it Ralph will overtake the Stitch building. I can also see a new large scale 100 year parade announced. Wild card here would be Frozen Land expansion.
Animal Kingdom: DAK is next on the list as far as Capital Investment. I can definitely see a new E-ticket announced for Dino land. Maybe even Excavator or total re-theme of area. I also see a new land/expansion announced. Could go many different directions: Zootopia, Indy, South America, etc. Will include another E-Ticket. Wild card - Updated or Alternate version of Pandora Avatar with new films on the way. Prob not going to happen but DAK needs a Lion King Dark ride. I mean come on, how can Lion King not be at DAK. Construct large Pride Rock façade and then a trackless dark ride using Hong Kong Beauty and Beast tech for attraction.
DHS: Not much here. Some stuff on Fantasia and maybe the future of Rockin' Roller Coaster. Wild Card here would be a new Indy Attraction to create a land next to stunt show. Could use the Shanghai boat ride tech for this new attraction. New film on the way! Also, could see Animation Courtyard overhaul but I think that is further down the line.
Out west: Updates on new Toon Town, Tron coming to Disneyland and the confirmation of Marvel E-ticket attraction coming. Maybe some small stuff on Disneyland Forward project.