I have a hypothesis that either...
A) Cid will be gone from school and be Shadow for some times until Diabolos defeated
This will result in his increase of"Mob reputation", and will considered died as a "Hero". He would no longer be a "Shadow" but a "Ghost"
Or
B) Cid will be back after his Agent "save" him under the disguise as "Medic"
This will impact his "Mob reputation" and become less of a "Shadow" and more of a "Hero"