If List of film trilogies is moved to series with three entries along with everything else then this isnt an issue  Only reason its getting special mention is that it is an accepted word unlike most of the others  If you were to accept octalogy as a word then few of the entries in that category would count as an actual octalogy merely a series  Think what Im trying to say is that all the above moves should be treated the same even trilogy which may prove a sticking point for some