Excited to do as you please and go anywhere you fancy in Metal Gear Solid V: The Phantom Pain? You can do that with the game’s free-roaming game design but not during missions, sadly.
This little tidbit of info was revealed by Hideo Kojima himself during his most recent podcast (Kojima Station Episode 26). In it, it mentions that players can go anywhere while they’re in free-roam, but once you’re in a mission, there will be a specific mission area that the player can’t leave, or they’ll fail the mission they’re in.
Players who are in free-roam can opt to do side-quests or other activities, which should alleviate the disappointment of those hoping to go wherever while tackling missions.
MGSV: The Phantom Pain will be released sometime in 2015.