Using context clues I’d say that means his time as Batman is just as done as Henry Cavill’s time as Superman, the difference being that Ben Affleck might just come back to direct a DC superhero movie.
This isn’t the first time he was planning on directing a DC film. The Academy Award winner was also in place to direct his own standalone Batman movie, which he described as focusing on the “world’s greatest detective” side of The Batman. He ultimately couldn’t find a script he was happy with and ended up passing the reins over to Matt Reeves who did his own version of that as a total spinoff from the established DCEU.
Affleck is a pretty phenomenal director. “Argo,” “Gone Baby Gone,” and “The Town” all stand out as the work of a confident storyteller who knows how to focus on the character first.
As far as the “right project” goes, it does sound like Gunn really wants to get Affleck in there, so he knows how much of a win that’d be for the new and improved DC cinematic universe. What could that right project be? How crazy would it be if Affleck got to direct his Batman movie after all, just without having to don the cowl as well?
It’s a time of change for the DCEU. We don’t know whether or not that change will be for the better or the worse, but it’s clear that Gunn and Safran aim to disrupt the DC status quo. However it turns out, it’s an exciting time.