As the internet boils over into an Ouroboros of speculation over the GTAV trailer, the full statement from Rockstar is brief and to the point:

Developed by series creator Rockstar North, Grand Theft Auto V heads to the city of Los Santos and surrounding hills, countryside and beaches in the largest and most ambitious game Rockstar has yet created. A bold new direction in open-world freedom, storytelling, mission-based gameplay and online multiplayer, Grand Theft Auto V focuses on the pursuit of the almighty dollar in a re-imagined, present day Southern California.

Other important notes: 1) We will now be calling this game “Gee Tav”. 2) PCG’s explanation of the multiple protagonists theory seems solid to me.