The full reveal of Metal Gear Solid V: The Phantom Pain has been full of mysteries and a bit of confusion, but Geoff Keighley of Game Trailers interviewed Hideo Kojima for some clarification on the matter. In the interview, Kojima explains the reasoning behind all the secrecy, as well as the decision not to use the iconic voice behind Snake, David Hayter.
As far as the Phantom Pain trick goes, I'd say Kojima's mission to get everyone buzzing and speculating on social media was a success. It's interesting to learn that this campaign has been in the works for so long, and that one of the intentions of the original mystery trailer was to "evaluate the FOX Engine," since they knew everyone would be putting the video under a magnifying glass.
And then there's David Hayter, whose voice is so closely associated with Snake. As some of you may know, Hayter said he wasn't approached to be in Metal Gear Solid V, but Kojima has a good reason for this. Though he can't say who, a new person will be playing Snake this time in another move toward making MGSV the start of something new for the Metal Gear series.