I think the return to the Shire MAY be in the Director's cut if anything at all... I, being a hardcore Tolkein fan, will be really disappointed if it is not in the original movie, but in a theatrical sense, it doesn't fit in the movie. The movies have been very action oriented and not very epic in the traditional sense. The general public will not realize how important and meaninful the return to the shire is to the original storyline.
One of the biggest reasons I believe it will be cut from the movie, is that the initial scenes in the Shire were cut down tremendously from what were in the books. There was no development with Frodo and Bilbo and their relationships to the other members of the Shire. The Shire is simply a hometown in the movies, a place to return to once the evils have been defeated. In the books, it was much more than that, it was a place with many stories to tell and a lot of history. The books fleshed out the town much more, and were reference throughout the story as a whole. I think if anything, the return to the Shire will be a 5-10 minute "wind down" after the climax of the war and the destruction of the ring. Frodo and Sam will return to the Shire, show them rebuilding, and most likely show them a few years down the road with family/friends. I really hope the Director's cut will show some of the events that happened in the book. In particular, the defeat of The Boss and his gang of thugs (you all know who he really is). I'd love to see the Hobbits kickin some thug ass, but I'm not gettin my hopes up.