If you pause the video at 0:32, you can see that the highway sign says Los Puerta. That, among other things, make it clear that this is a remake of Los Angeles, just as GTA IV featured a remade New York City. Not much has been said about the gameplay, but I wouldn't expect the drastic departure from the usual run and gun style that have made the other games so popular. This is one of the few times that I have been excited for a game right when the first trailer has come out. Here's hoping that this will be yet another Game of the year caliber game put out by the powerhouse studio, Rockstar.