Agreed. Edgar being the Ranger just wouldn't make a whole lot of sense. He doesn't seem to know what's going on, and he isn't the type to go off on his own and make stuff happen without telling Graham. Besides, the Ranger knows exactly what's going on and seems to be someone who was around when the evil got imprisoned. While I guess Edgar could be pretty old, seeing as how he's a fairy, I don't think he's that old.
So, I for one would call foul if the Ranger ends up being Edgar in disguise. I would like to see more development for Edgar besides him just moping around though. I know he's never been a man of action. He's more a walking personification of victimhood, but still, I'd like to see him do a bit more than pine away.