The door is open that he may have been killed by a temporal agent in that bar fight in Morocco? Since, even though he never mentioned it, it makes sense for Rios to want to meet Zefram Cochrane and witness the events of first contact unfold. And he can’t run into Picard during first contact, as he’ll tell him about the future. So a temporal agent would intervene to prevent that event from occurring. Sure, Rios could wait unit Cochrane gives that commencement speech at Princeton to meet him. But based upon what we know about Rios, he does not seem like the person that would wait until then. Thoughts?