I really hope that HS will stay with the theme of being a working studio. I don't want WDW to be a collection of parks with big coasters. I want a unique experience in each of the four parks. That is what makes WDW different from other destinations.
My dream for the backlot tour would be to expand it into a full Hollywood experience - one that follows a theme of what it takes to produce a movie - either animated or with live actors (or both!). The tram would include stops at key "attractions" where guests would depart the tram for an experience/show, then re-board the tram for the next experience. And, some experiences could be on the tram itself, similar to what exists today (e.g. Catastrophe Canyon). The tour could start with a stop for how movie ideas are born, and then progress through casting/costumes, special effects, actual filming experiences, editing and sound effects, etc.
Examples of stops/attractions would include audience participation opportunities, walk-through experiences (costuming, etc.), experiences on the tram, a "filming experience" (where you get to see how a spot in a movie is made), a working show (Indy, Lights/Cars/Action, or similar), etc. Oh, and think of how the tour might have an early stop for casting, where the audience actually auditions for various roles that would take place along the tour at different stops.
One example of a new special effects attraction could be something Star Wars related. It would be an experience/show, and not a ride. Something like either the ET Adventure or Star Trek Adventure that Universal used to have. The audience needs to be immersed in both the story and also in how the movie is made, with opportunities for volunteers to participate. That could replace the Pearl Harbor Green Screen show in the current tour.
And, if there was a way to let guests enter and exit the tour at any point, that would be even more awesome. Yes, that would be a lot of work/coordination, but what a way to present a studio! That would be a fully immersive backlot tour.
HS would still have "stand-alone" attractions not on the tour, such as TT, RnRC, TSMM, Fantasmic, etc. I'd like to see a new attraction that let's guests have an opportunity to be hands on for a filming sequence. Let someone run a camera, another the switcher, someone be a director, others be cast, etc. Simple, short roles, but it would give the guest the experience.
Well... that is my dream for the backlot tour