Than chance of Activision sue someone for that domain is very unlikely. As long as the owner is not misleading people to believe it is an official site or trash talk call duty, the website will not even be even on Activision’s lawyers’ radar. There are thousands of website with the games name on the domain and I never read about any of them getting sued.
The domain name could be worth a lot since
CallOfDutyForums.com, CallOfDutyForum.com, CallOfDutyForum.net is not being used.