It seems pretty obvious that the vehicle rooftop fighting shown there won't be the entire game, merely a part of it. They wouldn't step back from a true 3rd-person action game to something that's virtually a rail shooter.

While I'm not interested in the GoW series, that trailer looks impressive. Good range of moves, too - I liked the range of tactical stuff, like firing from cover and using enemies as meat shields. The whole 'gun with a chainsaw' thing still seems absurdly macho, though that's quite possibly the point.