I browsed the web and found this..
POSSIBLE MAP?
(http://i852.photobucket.com/albums/ab86/mansenmann/gtav-fake-map-1.jpg)
POSSIBLE PICTURE OF GAMEPLAY?
(http://i852.photobucket.com/albums/ab86/mansenmann/maphud.png)
DETAILS OF THE PICTURES:
If you see on the "Possible MAP" and look below in the shadow background, you'll spot palm trees, which is a detail that refers to L.A(Or as in GTA, Los Santos). Also, as Dan Houser said above that the Country side will be HUGE! You can see many different county towns on the map. Dillimore, Palomino Creek, Blueberry, Montgomery probably.
But the little island? Where did that come from?
If you look to the "Possible Gameplay" picture, you'll spot that the character is white? And still we see in the trailer that a black guy is running away from the cops, also if I am right, you see that it is a black guy that evades from the police in a red sport car. But, in the beginning of the trailer, the voice "Why did I move here? I guess it was the weather..." was a white males voice probably.
And as you see in the background of the picture, it is palm trees which is probably from Los Santos. Also if you look down to the left corner, you see that the HUD mod looks exactly the same as in GTA IV, the differences is that the armour and health bar is light blue(aqua) and orange, but the graphic shows twice as better as in GTA IV.
Also on the "Gameplay" you can look a little bit above the blue buildning with yellow stripes at the blades, you'll see a building that is white/silver with dark windows... Is that Star Tower?
Discuss..
(http://www.itp.net/images/content/580233/article/5292-fake-sta_article.jpg)