Project Casting has a post up on the Matrix 4. Carmen Cuba is the casting director via IMDb. Anyone interested in a speaking role will need an agent – no surprise there. Once production is close to starting, casting calls for extras will most likely start to appear. They are reporting that the film will shoot in Chicago beginning in February 2020.
Note: For now, I’d take that start date with a grain of salt. The initial start dates and locations that Project Casting reported for Bill and Ted 3 turned out to be incorrect. Nothing is currently known about the script. For the other films in the Matrix franchise, the shoots were long. For John Wick 4 to be completed in time for its May 21, 2021 release date, I’d expect that shoot to begin in summer or early fall of 2020. If Matrix 4 is going to shoot first, then it will have to be in a window of time that will not interfere with JW4, IMO. Also, if there will be a lot of action in Matrix 4, it will have to leave enough time for Keanu to recover from the shoot and train for JW4. And with that and $1.50, you can buy an awful cup of coffee at the local convenience store.