Oh it will be definately be nominated, as the other two were. And Peter Jackson will be nominated for Best Director.
I forgave the first two movies being passed over for the ~winning~ of those awards... because I understood that they would not want to set a precedent for the films dominating awards three years running, or award the early film and not the last. I fully hope and expect for the academy to award Best Film and Best Director for this one as a way of acknowledging all three.
I think it deserves it, and I think the actors will want to award the studio and the Director for going to the sheer dollars, attention and effort these guys went to just to give actors a grand environment to act in. Sure, they have already been rewarded with money... but I think they will always want the accolades of their peers, and Hollywood will want to encourage other studios to spend big money on "big" epic movies.
That's my theory anyway, and why I will have my fingers crossed.