Fellowship of the Rings: 178 minutes / 208 minutes extended edition
Two Towers: 179 minutes / 223 minutes extended edition
Return of the King: 201 minutes / 251 minutes extended edition
If Return of the King proved anything, they could easily make the first movie three or more hours to fit it all in. If not, I think there is plenty of content to have the first movie end when the party is captured by the wood elves. Then the second movie could cover from there on. Since in the book we don't "see" the entire battle of the five armies, they could extend that part for the movie.
If they don't choose to do this, they have plenty of history to work from to make a sequel. It won't be nearly as good due to the lack of a book, but it could still kick all kinds of ass. Christopher Lee could come back as Saruman and we could follow his fall to darkness. Gandalf looked old as hell in the LoTRs movies, so not much makeup would be needed. Ian Holm would only have to look like he did in the first movie, because remember he looked like he "hadn't aged a day".
My only fear is that I will have such utterly high hopes for this movie, it won't be possible to live up to them.
To be honest,
The Hobbit (1977) (TV) wasn't all that bad. If you haven't read the book, even though I highly recommend you do, you could always watch that.
