I also think we shouldn't rule out Snow White and the Huntsman, James Newton Howard has gotten plenty of surprise nominations in this category.
Other than that I think this category is impossible to predict, because some year's its extremely predictable and others you wouldn't have expected any of the nominees.
I know I'll change my mind before the Oscars, but the safe line-up:
Life of Pi
Zero Dark Thirty
I mean I could see all of them missing except Lincoln. And I do think Argo is more likely to be here than Zero Dark Thirty.