With games like Battlefield 3 pushing the boundaries with its game engine, one would expect the new Call of Duty game to finally receive a new and improved game engine with the latest bells and whistles. Unfortunately fans are going to have and wait; during an interview Mark Lamia confirmed that BO2 will be using the original Black Ops game engine from 2010.
Mark Lamia, Treyarch: "... the answer may not need to be an entirely new engine, but you might need to do an entire overhaul of your entire lighting system. The trick is, we're not willing to do that if we can't keep it running at 60 frames per second - but we did that this time. So this is the Black Ops II engine."
Basically Treyarch wants to keep the game running at 60 FPS, but to do this, the game engine needs to be toned down. Luckily the entire lighting system has received a complete overhaul, which should make up for it, as seen in the teaser trailer 2 weeks ago.