For being only the first trailer, it revealed a lot of hints that point towards the whole San Andreas map being in the game. The huge mountain that looks like Mt. Chilliad and the desert with windmills. I think there's a hint that Las Venturas will appear in GTA V. Look at the screenshot, it shows what looks like a liquor store with gambling symbols that's out in the desert outside of Las Venturas. To me the huge mountain and liquor store in the desert are hints of San Fierro and Las Venturas being in the game. Think about it, from Los Santos when you're on your way to San Fierro what do you see? A big mountain called Mt. Chilliad, or on the way to Las Venturas what do you see on the way there?