J.J Abram revealed he'd like to make a Star Wars anthology film focusing on the Knights of Ren in an interview with Collider. When asked what Star Wars anthology film he'd love to see, Abrams responded "I gotta say Kathy Kennedy, who’s running it all, she seems to be pushing all the right buttons. There isn’t something that I’d love to see—I guess the one thing I would say is there’s a Knights of Ren story that I think would be pretty cool to tell.”
"The Knights of Ren" is an organization under Supreme Leader Snoke and their ranks naturally include the main antagonist of Star Wars: The Force Awakens, Kylo Ren. This organization only appeared breifly in the movie and we don't know much about any of the other members besides Kylo. However, it seems that Abrams has a specific story in mind involving them.
Right now there are no indications of J.J. Abrams returning to the Star Wars franchise as a director to make such a movie. He stepped down after directing Star Wars: The Force Awakens and is being replaced by Rian Johnson for Star Wars VIII. However, he is still a producer for the upcoming Star Wars movie.
A Knights of Ren feature would likely give us more of an idea what happened between The Return of the Jedi and The Force Awakens, which is an intriguing prospect. It would also be a Star Wars movie that focused on villains in a way other films haven't. Of course, the prequels showed Anakin Skywalker's fall to villainy, but he was a tortured hero for 95% of those movies and only went full villian at the tail end of the third one.
Would you be intrigued by a Knights of Ren feature? Would you like to see J.J. Abrams back as a director? What other kind of anthology movies would you like to see?