Konami have been reported to say that Raiden is in fact dead. That's why his bottom lip and eyes are black and not there usual color. What they say about Fox is that he was close to death but was brought back to life so in all fairness he was dead until they placed him the the suit. Olga could live without the suite Fox and Raiden can't. They are incorpreated into the suite which means they are prity much dead and not a living being. Like Fox I don't think Raiden opted for this but was also near death when he was placed in the suite.
Metal Gear Solid 4: Guns of the Patriots, Raiden appears wearing a cyborg ninja exoskeleton and fights several Metal Gear GEKKO units armed only with his high-frequency blade. According to lead character designer Yoji Shinkawa, Raiden is "falling apart" and has had most of his body parts replaced by cybernetic prosthetics. Hideo Kojima has also stated that his blood is no longer red, accounting for his pale appearance. In a recent MGS4 trailer, Raiden engages Vamp in a duel. Raiden fights recklessly by being stabbed multiple times by Vamp before impaling himself with his blade in order to injure Vamp. The fight sequence ends in a stalemate with Vamp and Raiden stabbing each other. They have a brief staredown which ends with Vamp asking Raiden if he will be the one to finally finish him. Although Raiden will not be a playable character in Metal Gear Solid 4, he will be constantly present throughout the game serving as Snake's backup. He will reportedly be playable in the next iteration of Metal Gear Online, a stand-alone game set in the MGS4 timeline.