User blog comment:MerlinNimueh/Returns/@comment-4135736-20111221090648

The only character who I think should return is Mordred because he is the biggest threat to Arthur as he is destined to be his doom. He must return in Series 5.

Morgause and Nimueh are past so I think they have met their final defeats, especially Morgause because they need to focus more on Morgana who needs to make her own decisions more often rather than listen to her sister.