The IW Engine was first used in Call of Duty 2 (2005). It was used in Call of Duty 4: Modern Warfare (2007). It was used in Call of Duty: World at War (2008). It was updates sometime in 2009 to the IW Engine 4.0. The update featured the ability to make a more detailed environment. Call of Duty: Modern Warfare 2 (2009) used the IW Engine 4.0. Call of Duty: Black Ops (2010) went back to IW Engine. Call of Duty: Modern Warfare 3 is going to be using the IW Engine 4.0.
What does this all mean? Nothing really. People will still play Call of Duty like it is the best multiplayer experience ever. My question is, when is the Call of Duty series going to add something innovative? The series doesn't need a completely new engine because Call of Duty 4 used the same engine as Call of Duty 2 but look how innovative it was. Maybe if Activison can implement dedicated servers and maybe the developers can recreate the multiplayer again (like IW did with Call of Duty 4) and Call of Duty can feel fresh once again.
Some examples of slight innovations the developers can add to series (to compliment the dedicated servers) to make Call of Duty feel fresh again are:
- Reinvent/Remove the perk system.
- Add an in depth character customization system (more customized than Brink or Halo: Reach) Maybe it can make use of Kinect to add your face to the game.
- Make the guns more realistic (make the guns have true recoil).
Unless I see some kind of innovation/dedicated servers I will not touch the multiplayer. Right now Modern Warfare 3 is a 2012 weekend rental to play the campaign and that is it.