the developers started GoW3 just after they finished the 2nd game, they've had 2 or so years to develop GoW3, and being a 1st party developer they are privi to all the best internal tech which would allow them to build a great graphics engine from scratch while the content was made for the game in parallel, plus they had allot of funding from Sony, this is just my assumption.
I honestly don't see Sony destroying one of their great games for the sakes of rushing tha game so it can be out by this year.







