User blog comment:Crazy sam10/Call of Duty: Ghosts Teaser Trailer released/@comment-58.168.41.102-20130502113251/@comment-5081943-20130502152619

And yet nobody ever complains about Valve's Source Engine...

Seriously, there is no such thing as new game engine. So-called new engines are just big upgrades to the old ones. Making a new engine from scratch would take 2-3 years. Time that Activision doesn't allow either IW or Treyarch to have.