User blog comment:B214/Question and Answers 6/@comment-134.115.183.214-20160731121507/@comment-9595671-20160731130458

I wouldn't fully say that, Trihexa is still a threat in another manner, the fact someone could attempt to get him out again. So the final enemy wouldn't be Trihexa directly, but the threat of him getting free.

Though ultimately I doubt Trihexa himself will break free unless all the events in EX end up being non-canon or some details werne't mentioned truthfully for spoiler reasons. I doubt they'd want EX to reveal that Trihexa is dead because that also spoils what happened to everyone trapped with him.