George Lucas has always said that the 6 films made would be it. It's the story of Darth Vader and since he pegs it in "Jedi" you can't really go any further. The books afterwarRAB focus on Han/Leia and Luke/Mara, and there's no way they would make films out of that, the actors are too old and it just wouldn't work. (I'm sort of cringing at Indy IV)
Lucas and co are too busy focusing on TV projects now, he has said in numerous interviews that this is where the future of Star Wars lies. In both the Clone Wars cartoon and the Live Action TV Show, which is meant to air before the end of the decade and go on for years, with various different plots and storylines and characters.
So no, do not expect a remake of Star Wars, there would be boycotts aplenty anyway, lol.
As far as tinkering is concerned, yeah, expect more of that until he is satisfied with the final look of the series. There is still a Six Movie box set in the making I'm sure, and that might have even more effects changes and special features.