We've known for a while that original Matrix cast members Keanu Reeves and Carrie-Anne Moss will be coming back for the fourth Matrix movie, and though Hugo Weaving won't be able to reprise his role of Agent Smith, another franchise vet will be making his return in the upcoming sequel.
According to Deadline, actor and stunt performer Daniel Bernhardt will be making a comeback as the lesser-known Agent Johnson. We don't really know how large the role will be for the sequel, but I can expect that Agent Johnson will be the closest thing we get to a return from Agent Smith. Since Bernhardt's casting was announced late, I have a feeling his role is only going to be minimal, but it would be great to see him match blows with Neo again.
Besides the returning cast members that have already been mentioned, Jada Pinket Smith will also be coming back to reprise the role of Niobe. We don't know what her role will be exactly, but since it is hinted that she resumes her romance with Morpheus, it's likely she's going to be filling in that role in some form.
Though a lot of franchise vets will be making an appearance in the film, we should expect to meet some new faces in The Matrix 4 including Nel Patrick Harris, Jessica Henwick, Jonathan Groff, Priyanka Chopra, and Yahya Abdul-Mateen II. We don't know what their roles are for now, but it's assumed that Abdul-Mateen will be the new protagonist this time with Neo passing the torch of savior to him.
Then again, this is all just speculation. Hopefully we get some official reveals before the year ends.
The Matrix 4 is set for a release on April 1, 2022.