Both presentations will be held at The Anaheim Convention Center in a 4000-seat arena.
The D23 Expo would seem to not be using the entire capacity, probably customizing to accommodate staging and backstage areas.
This temp theatre will probably also be created using custom seating based on the screen and sound capabilities, etc. It would be surprising to see it hold over 3,000. Plus there are typically a certain number of seats set aside for various studio guests and media.All other film screenings and programs will take place in The Walt Disney Studios Theater (at the Anaheim Convention Center), a custom-built state-of-the-art venue with 3D capability, located within the Convention Center.