So I've read through all these wonderful suggestions. Here is my take if you don't mind. If Disney does indeed have the Potter attraction rights, it should definitely go in the Studios. It just makes sense. The Magic Kingdom is the "Disneyest" of all the parks and should contain only Disney movies, IMO. I know that doesn't fly with DL or DLP. Also a new Indiana Jones ride would fit in nicely with the Stunt Spectacular or even replacing it. Just because there is a castmember access road behind the stunt spectacular, doesn't mean it can't be moved. Look what they did with the road coming from the Magic Kingdom when the Racetrack was built; it moved over a bit. I don't think there should be too much concern over the parking lot. Remember that Disneyland Resort has the beautiful parking structure, not that there isn't land beyond the parking lot to expand.
To make this a true full day park I would definitely renovate the Great Movie Ride. This attraction celebrates the movies and should continue to be the premier attraction (everything doesn't have to be about thrills). Also, move that darn Hat out of the way and into the entrance area outside the park as a draw. The Chinese Theatre is a beautiful building. Don't hide it.
Since Disney has the rights to the Muppets, I would suggest dusting off the moth balls of the Great Muppet Movie Ride, which would be a great contrast to the original movie ride. Add a children's type ride (e.g., Dumbo style) in the area also.
As with Star Tours, updating it would bring a huge amount of people to the attraction. There have been three movies since it opened, technology has changed. It would also be a good idea to expand the area to include an eating establishment. How about a photo place so you can dress up like your favorite character.
While we're on the subject of moth balls, Disney should really consider adding the Dick Tracy attractions area. If there truly is room over on Sunset Blvd, then build it. The theming is there already, go for it. Change the entrance to RnR through the animation end as it has the same look (studio building). That would help alleviate the traffic problem down Sunset Blvd.
Finally, something needs to be added over by the new LMA show. Too bad a Hyperion Theatre cannot be erected. Then they could bring back my favorite show, Hunchback of Notre Dame. They could even bring Aladdin from DCA.
If Disney would only bring back the wonderful animators into their own building again. Life would be sweet.
So many other thoughts, but this post is getting too long. What do you think?