https://www.etonline.com/joshua-jackson-will-likely-not-return-to-the-affair-for-season-5-source-exclusive-110277

If Jackson does return, it will likely be for one episode, reports Entertainment Tonight, which adds that Jackson originally planned to exit the Showtime drama after Season 3.

Joshua Jackson Won't Appear in "The Affair's" Final Season
by Rick Porter
June 4, 2019


The final season of "The Affair" will run without one of its original stars. Joshua Jackson has officially exited the Showtime series and won't appear in the fifth and last season, sources confirm to The Hollywood Reporter.

His name was conspicuously absent from a press release announcing the show's premiere date of Aug. 25.

https://www.hollywoodreporter.com/live-feed/joshua-jackson-wont-appear-affairs-final-season-1215502