I think I recall the reason for Posetcoglou's sacking was the league position of 17th being unacceptable in the club statement on the matter. So the criteron for the sacking is there. Being 5th the previous season or winning the trophy last season, didn't sweeten the league position.
But I assume that was down to Levy, he's gone. I wanted Postecoglou sacked in January. I'd be shocked if we end up 6th with no trophy and Frank is sacked for it because it's worse than Postecoglou's 5th.
Imagine it will depend on how the team is performing and the style of play.
If 6th is where the club finishes though, and no trophy, then I dont blame some fans for being dissapointed.