If they do that, it'll just be too obvious and to me lame. I would rather it be the Tourist killers or Trinity or some unnamed guy because that killing just seemed odd to be over deb cheating on him, and some say it's Quinn but that's stupid too.
I've been hearing or rather reading that some are thinking it's Trinity's son. I don't know how I feel about that yet but we only have 6 episodes to go so we'll have all the answers soon, although it would be cool if they throw us for a loop this season and not have evreything wrapped up by the season finale. Not a cliffhanger per se but leave some burning questions going. Oh, I also read poeople think the reporter chick did it, people are just throwing out crap like Lost fans hoping to get something right. lol