Its really going to depend on what is inside the Game Informer magazine. Considering we're going to find out about the main protag(s), and story. I will be content with an awesome trailer showing of more of the countryside, and something new (depths of ocean? Rockstar just embellishing). I'm sure they're going to give us a lot to talk about.
About goddamn time haha. As I read from a user in a different topic, I think another voice over of "why did I move here..." would be quite cool, seeing as there is strong rumours of a second playable character.
Just hearing of how three characters are juggled during game play is alone, pretty interesting, but I have to say, first and foremost, more of the vehicles and the map showing the ultimate scale of it are what interest me most, HOWEVER, I would imagine the plotting is key in further trailers, but remember, they won't be in sequence either. Another key of contention is children showing up in any GTA, we know now that there will be or proposed to be Teenagers, but not Children below a certain age, so this is certainly a new aspect for GTA as a franchise, and we also know of one dog, but other then that, just rumors as far as animals found throughout the game!!