Sorry to double post, but something occurred to me afterwards, I was thinking about the blood on the what we think is Jake's hand.
If the franchise is to continue wouldn't it make sense for the main protagonist to be Jake Muller, taking up his father's position, Sherry is being sent to protect Jake so conceivably in the short time together (in game and the time scale it is set in) they could form a bond, something happens to her could make him snap, change sides, call it what you will, would be a perfect way to have this mercenary change allegiances.