Although the next entry in the Call of Duty franchise is yet to be officially announced (it's believed to be a group effort involving Infinity Ward, Raven Software and Sledgehammer Games), there is some news regarding Treyarch's next Call of Duty title, although no formal announcements have been made by the Black Ops developer.
According to the developer's career page, they are looking for a Gameplay Combat Designer. Highlights of the position listing include:
This position reports into the Design Director for the Call of Duty multiplayer team at Treyarch.
Working with high level design direction, the ideal candidate will design, develop, and tune game mechanics and features, largely in the area of combat systems (such as weapons and attachments) and gameplay mechanics (such as Perks and spawning).
Another listing, this time for a Scripter, requires the applicants to "be an expert on first-person shooters and trends of the genre." The listing also includes a little note about qualifying for the position - "A design test utilizing Call of Duty mod tools may be required depending on previous experience."