Call of Duty has proven itself highly resilient to series fatigue. While the quality of each entry has varied wildly for at least a decade, its overall popularity hasn't been in serious doubt since Call of Duty 4. Perhaps this is because Call of Duty is so culturally omnipresent it would require active effort from Activision (and now Microsoft) for it to fail, but the series has also demonstrated a knack for evolution, introducing new settings and new multiplayer modes in response to changing tastes.
Nonetheless, it seems concerns about series fatigue are beginning to seep in, at least over at Black Ops handlers Treyarch. When asked about the issue by CharlieIntel (via Eurogamer), Treyarch's senior of director of production Yale Miller responded: "I think the honest answer is yes, I worry about that."
