I am pretty sure that we will see changes to all six movies. Since George Lucas now has time to step back to get the whole picture and adjust it were he sees fit. At one point in time though, he will have to nail it down and say "Ok, this is how I want the saga to be remembered."

In my opinion, he should publish a "StarWars construction kit" containing all source material for all the starwars films in a ready to be implemented state - so everyone can tinker around with it like he does - at least we'd all get a chance to have our way and build our favourite version of the films.