First and foremost is the budget which, though Warner Bros. have placed a lot of faith in Jackson to prevent this, still runs the risk of spiralling out of control. With the budget for the first two films set at a cool $500 million, the third is set to cost less since some of the film's material has already been shot when The Hobbit still stood as a two-parter.
Another issue is the script, which doesn't exist in its entirety yet. Jackson and his fellow writers, Fran Walsh and Phillippa Boyens, will have to consider that the first film will now have to prepare the way for events in a third film which may not necessarily exist yet. Shooting on the first film has been extended from June for pickups on "battle stuff" so there is an opportunity to add in anything essential.
There has also been an image released of the limited edition 3D glasses that will possibly be given out for screenings of The Hobbit: An Unexpected Journey.
They don't look like the most comfortable ocular devices I have ever seen and are quite frankly pretty bizarre. I'd have personally gone for John Lennon style circular specs with thick gold rims to look like the one ring itself, but then again, I'm no glasses designer.
The Hobbit: An Unexpected Journey is released on December 14 with part two, The Hobbit: There and Back Again due on December 13, 2013 and the as-yet untitled third film arriving in summer 2014.