I don't think there's any point in continuing. It's like trying to stay on a ship that is sinking. If it does continue, I don't understand where they story can go. Tosh and Owen are dead, Ianto is dead, Jack is who knows where (we don't even know what mental state he is in). As for Gwen she'll have her baby and move on eventually. There's no where to go anymore. They could have done something more; but RTD rather of had an nihilistic, the evil aliens are taking over the world for a billionth time movie of the week.