I think if you have 100GB of space, the movie would just be less compressed. Usually the space taken by the film just expands to fill whatever new ceilings are offered. You could technically fit three versions of Star Wars on a DVD, it just wouldn't look very good. And you could do the same with Blu Ray now. While a 100GB disk would present pretty good quality even with three versions, next to other 100GB releases that don't need to fit three films on one disk it would look poorer, so you'd want to increase the file size of the film to fit the expanded ceiling.