A little update: during a recent interview, Anderson expressed his annoyance about Fox's constant cutting of the movie, and slapping the early release date on him. Also, he confirmed that there will be an R-rated Director's Cut, with quite a few more on-screen kills and a whole entire subplot that had to be cut from the theatrical release.
You can take a look at the article here:
http://www.imdb.com/title/tt0370263/board/flat/11022775
Not entirely sure how legit it is, but it's worth a read.