I expect the final (theatrical) cut of ROTK will be about 4 hours. Wow, to have to cut 1/3 of the material to get it in the theater. Hopefully, we won't have to wait too long for the Extended Edition to come out.
Alternatively (dreaming here), Jackson could go back to New Line and have them release the six hour cut as two different movies AT THE SAME TIME (or at least within a very short time frame). I would have no problem with LOTR being a 4 "movie" epic.
My wild and fond hope is that the movies will be so successful that there will someday be a 'director's cut' for all three movies and that Jackson will be able to put absolutely everything he wants into them. I personally, would be happy to pay hundreds for such a collected special edition :)