The Academy Award for Best Production Design used to be called the Academy Award for Best Art Direction until this year. I personally prefer the old name, but an award is still an award.
Let's look at the nominees:
The Hobbit: An Unexpected Journey
Life of Pi
My personal choice is going to be Life of Pi for this award. The art direction of the film is really great, and everyone has been raving about it. A few image searches on Google will show you why this is the case. Also, I previously mentioned that there is a trend for one film to win at least three technical awards, and Life of Pi looks like the most likely movie to win at least three technical awards this year. I wouldn't be suprised if Anna Karenina were to win, but my bet is on Life of Pi.