The UK Official Playstation Magazine has released more information and this game sounds intense. Here is the newly released info.

 

First off, it seems the Chimera will be targeting the San Francisco Bridge and other recognizable American landmarks during their U.S. siege. But first Captain Nathan Hale will continue where the original story left off, and he’ll find himself in Iceland, home of the SRPA (Special Projects Research Administration). There where he will find he is not alone... Other humans have also been infected with the Chimera DNA and have obtained mutant healing and even telepathic abilities. Some of these now-special humans have come together to form the Sentinels; a task force designed specifically to hunt down the Chimera.

 

Here’s a summarized look at the other info that popped up in the feature article: There will be three character classes for co-op play: Soldier, Medic, and Special-Ops. Each will collect experience to improve their own special set of skills. One of the new weapons is called the Splitter, which is basically a super-powerful minigun. Killing the aliens has a benefit.  The more you kill, the more you can "charge up" your abilities, I’m assuming like Ratchet and Clank. The new Stalker has been redesigned and given new functionality - huge, fully dynamic bosses that have to be taken down differently than standard enemies. Keep tuned for more info from ps3 court.