Technically CoD is developed by two different development teams. Infinity Ward makes the "official" CoD's that maintain the numbering sequence, and Treyarch develops the offshoot CoD games, like World at War and Black Ops. They're not developed together, so each CoD game is developed for around two years.

Activision are the ones ****ing over games like CoD, not the developers. Activision considers everyone as expendable and if you're not churning out **** as fast as possible for them they'll just toss you aside and find someone else to do your job. The fact that these games have absolutely ANY innovation at all(for example the Zombies game appearing in WaW, Black Ops 2 having a drastically overhauled class system[one that has remained largely untouched since Modern Warfare], and trying out a new setting) is somewhat amazing; because if I were the devs I wouldn't give a single **** about the quality, yet they seem to at least try. The original Modern Warfare team were ****ed by Activision and fired, so they have formed their own team of developers so let's see what they can do when they have some freedom to do something new for a change.