Is modern warfare 3 on the same engine that the last 2 were one?

Solution 1:

Modern Warefare 3 is running on the IW engine this engine was originally based off the Quake 3 engine created in 1999. This engine has gone through several different versions and has been used for several different games.

• Call of Duty 2 (2005) IW 2.0
• Call of Duty 4: Modern Warfare (2007) IW 3.0
• Call of Duty: World at War (2008) Modified IW 3.0
• Quantum of Solace (2008) Heavly Modified IW 3.0
• Call of Duty: Modern Warfare 2 (2009) IW 4.
• Call of Duty: Black Ops (2010) Modified IW 3.0
• GoldenEye 007 (2010) IW 3.0
• Call of Duty: Modern Warfare 3 (2011) Version number is only listed as MW3. An interview with one of Infinity Wards creative strategists said that it is technically IW 5.0

As to whether it is dated or not is a bit of personal opinion. In my view it is pretty outdated these days.