Call of Duty: Vanguard is about to launch, but that doesn't mean next year's installment isn't already being worked on. With multiple studios working on Call of Duty, it's always possible for a game to be in production.
Based on leaks, the project is internally called "Project Cortez" and will be a sequel to Modern Warfare 2019. The leaks are based on the NVIDIA GeForce NOW information. In the leak, there was an unreleased project titled “Project Cortez — Activision Blizzard — Infinity Ward.”
Modern Warfare 2019 had mixed reviews when it came out. While it could be described as the most successful Call of Duty based on sold copies, professional players had plenty to gripe about. Everything from gun mechanics to spawns on maps, pros in the CDL were not happy at times.
Other than the initial leak, not much else is known about the upcoming Call of Duty project. This is to be expected as Vanguard hasn't even launched yet.