The quick answer — which I will largely ignore for the rest of this post — is no, because in this day and age of Internet spoilers, a main character's departure from a show would most likely be widely known by airing. Some keep their secrets better than others ... Also this was done very well in Life On Mars, Brit version, which allowed the series to actually conclude utter satisfaction. Last example I can think of off the top of my head is this past season of Primeval. ...
