* JJ's Departure: JJ left the BAU at the end of season 11, but returned in season 12.
* Season 16: The most recent season (16) was the last one, and it had a satisfying conclusion for the team.
* No official word on a revival: There have been no official announcements about a new season or a return of the character.
* A.J. Cook's other projects: A.J. Cook, who plays JJ, has been active with other projects since Criminal Minds concluded.
Therefore, it's impossible to confirm JJ's return. The best way to find out would be to follow any official announcements from the creators or cast.