Even though Randy Orton is a top draw for the WWE, he won't win the Elimination Chamber.
In fact, he won't even make it through most of the match.
It would be easy to predict him eliminating Cody Rhodes or the obvious choice, the Great Kali. It just isn't going to happen.
Orton is at a place where he is willing to help other people go over, and Smackdown is in a creative place where new wrestlers are being pushed to the top. Mixed in with the unpredictability of the Chamber, the WWE has an excuse for why he should be removed quickly.
It would even help Orton's character and progression if he was to be eliminated first, and it would help Smackdown as a brand.