While this isn't technically breaking news I thought it would be nice to have a list of what we know will be happening in terms of the plot/structure of the films (sort of a compliment to the Confirmed Cast thread). The list is specifically about the plot/structure of the films, not other stuff.

1. There will be two films.
2. The two films will cover events in the timeframe of the book.
3. There will not be a "bridge movie" set between The Hobbit and The Lord of the Rings.
4. The filmmakers want to "expand" the story to include things not mentioned in the book that Tolkien thought of later.
4a. This presumably refers to the storyline of the White Council and Sauron's withdrawal from Dol Guldur.
5. The two films will be continuous parts of a unified whole which will itself blend with the LOTR trilogy.

Did I miss anything?

We know Sir Ian McKellen will most likely play Gandalf and Andy Serkis will play Gollum.

That's casting news, not stuff about plot/structure. You can check out the Casting thread for more about that.

What book did Tolkien put the story about the White Council and Sauron's withdrawal from Dol Guldur?

There is a very brief mention of it towards the end of The Hobbit and a few mentions in the Appendices of LOTR, but that's about it. For the idea to be fleshed out enough to be filmable the scriptwriters will essentially have to write fanfiction.

Well Eldorion, Tolkien left enough info about the White Council and subsequent events, that using the term "fan fiction" is a wee bit overstated . Fan fiction generally refers to some entirely new situation created out of wholecloth .

Sure, Jackson and Del Toro will have to write the story and dialogue, but the plot outline is entirely Tolkien.

GB

I was just speaking based on some fanfictions (fairly good I might add) that fleshed out parts of the story only alluded to - like the romance of Eomer and Lothiriel for example. I don't think fanfiction has to be entirely new, just a story set in an existing fictional world written by a new author (the exception being ghostwriters and people who are authorized to carry on the series like the guy finishing The Wheel of Time).

Point taken. Sometimes people use the term "fan fiction" in a derogatory manner. I didn't think you were per se. But I thought it might be misconstrued that way .

GB

Yeah, I wasn't trying to be derogatory and I'm sorry if it came off that way, but that's what I honestly think this is going to end up being if they really try to incorporate elements that weren't in the book.

I'm really excited about the Hobbit coming out, i don't suppose anyone has any kind of idea how long until it will be out? I know the cast is still yet to be finished!
I am glad Sir Ian McKellen is playing Gandalf, and i would really hope they cast Ian Holm who played Bilbo in LOTR, as i think he did a fantastic job and i couldn't imagine anyone else playing him!!!