By everything you mean everything except San Fierro and Las Venturas? Don't get me wrong, the game looks fantastic, and I'm sure they're gonna add SF and LV, but the initial lunch was lacking those two icon cities.
It's not that the map is small, it's that it doesn't seem (and I'm only speculating here, as I haven't played the game) as diverse as San Andreas was. The cultural differences between the cities in SA were grand, and even though it took you 2 minutes to fly across the map, it felt like quite a distance because of how different the cities were. There is no question the Rockstar worked their asses off, and that GTAV will be an amazing game, and that it will feel large.