4. Mexico City
Ever since I played Grim Fandango as a child, I've been obsessed with Mexico and the amazing decorations associated with Día de los Muertos (Day of the Dead) and whilst, the now Disney owned, LucasArts are unlikely to ever revisit their noir inspired, Land of the Dead, I think Rockstar should seriously consider setting their next game, at least in part in Mexico City. With GTA V's focus on Southern California and Los Santos, I would not be surprised to see the Mexican border make an appearance, perhaps in a similar fashion to Red Dead Redemption, which featured a small part of North Mexico, and one of the greatest uses of music in gaming history:
http://youtu.be/i8IonrlZp74. Such is my love of Día de los Muertos, that I'd love to see Rockstar include this unique experience into the game by setting at least part of the game during early November but I'd also expect to see Lucha Libre make an apperance and at the very least I want a heist mission involving the characters disguised as luchadors.