Brad Pitt is reported to star in Quentin Tarantino's tenth and supposedly final movie, The Movie Critic. Deadline states that it is currently unclear if Pitt will be playing the titular character, but it seems like he will be.
You don't really get Brad Pitt in as a bit-part, unless you're making Deadpool 2. The movie is set to release next year, but details have been pretty light on it. Tarantino has said in the past that the film was inspired by a movie critic that used to write for a porn magazine.
It's unclear how much of that original story will make it into the film, but it's likely Tarantino is going to take his time with this one. He's pretty adamant this will be his final film, but we can all see him coming back to the business in one way or another.