But he made a comeback last year with the success of Hacksaw Ridge, a World War II action movie that has gone on to earn the Australian more nominations at this month's Academy Awards.
THR says Gibson is "familiarising himself" with the material for Suicide Squad 2, but that the studio is being "passive" with him.
The first Suicide Squad did well at the box office, earning more than US$745 million at the global box office, and was the fourth highest-grossing movie at the New Zealand box office.
However, the movie was slammed by critics, earning just 26 per cent on Rotten Tomatoes, leading some fans to call for the site to be disbanded.
The sequel does not yet have a release date.