"Well look, at least I had a good run," Hayter tweeted today, likely after seeing the news himself. He also replied "nope" to another Twitter user, who inquired if Hayter was asked to reprise his roles as voice actor. Snake losing his voice is quite a phantom pain in itself, except for the whole Kiefer Sutherland part.
Update: To clarify, the supposed voice of Sutherland can be heard from the bandaged man that is guiding Snake in the trailer, not Snake himself. Presumably, another voice actor has replaced Hayter.
Update 2: Contrary to what Kojima said during the GDC panel today, Konami has confirmed with Joystiq that Ground Zeroes and Metal Gear Solid V: Phantom Pain are indeed separate games.