Based on clues from Hideo Kojima concerning the main theme of the story in Metal Gear Solid 5 the unoffical MGS site has managed to narrow down what it might be.
Kojima has invited fans to guess what it might be, "Question Gene (MGS1) – Meme (MGS2) – Scene (MGS3) – Peace (MGSPW) – ???e (MGSV). Answer will be revealed pre-E3 on 6/6," he asked on Twitter.
"Theme of Peace Walker was PEACE. Paz/Kazu (both mean peace) starred & was about deterrence as one of the method of keep peace in human society. The ending of PW was he/she's chosen deterrence in order to keep his/her mother-base. Theme of V is"???e". 2 characters in Kanji.
"PW was about deterrence, & peace as theme. Story of MGS3 was about the Cold War, & SCENE as theme. In MGSV [the story] will be about "??" & "???e" as [the] theme."
Based on what he's said the MGS site has concluded that the theme of Metal Gear Solid 5 will be based around a four letter word which ends in 'e' and is not love, hope or fate. The theme will consist of two kanji characters in Japanese.
While we're going to learn the theme at Konami's pre-E3 event later this week what do you think it might be in the meantime?
Regardless, it's now believed that David Hayter may be making a return to MGS5 as the voice of Snake after all.