He might win the King of the Ring which would probably be just to have Triple H have a big comeback and proclaim himself the real king of the ring. I Believe this story was setup some time ago, but do to Triple H not being ready it was put on hold. Remember Sheamus was sitting on a Kings chair thrown not so long ago.
Sheamus winning KOTR would be awesome, and a great way to conclude his 2nd year in the WWE. And as it's been said before, it would be the perfect way to bring the "King of Kings" Triple H back into the WWE going into 2011.
However, I feel that Sheamus is at a point in his career where he no longer needs to win KOTR to win another world championship, because we all know he'll have another reign under his belt by the end of next year. KOTR is sort of like MITB's older brother - it's the old-school way for WWE to push an up-and-coming mid-carder into the spotlight.
So for that, my personal picks are either John Morrison on Raw, or Alberto Del Rio on SmackDown. Daniel Bryan is US Champion, so he'll remain in that spot for a while. Big Zeke is a monster, but not main-event level yet. "Dashing" Cody Rhodes and Kofi Kingston are simply mid-card filler, etc.
Whatever they do with him (and King of the Ring is not really the way to go with him, I'd contend), they need to find something positive for him to work with, as they've let him get rather poor storylines since his feud with Orton wrapped up. He's actually getting the best reactions of his WWE run right now, and I'd say a face turn is downright inevitable, but you can just see WWE creative strain to give him something to do while waiting on Triple H to come back.