If you listen to Brother Vance, his makes the statement, "I am who you think I am.", referring to himself as Osiris. Luke Smith confirmed Osiris isn't dead in his interview this week. I do believe Osiris will play a large role in the expansions to come. The main storyline revolving around Destiny, revolves around the Vex and the Darkness. Osiris was on to something huge in regards to understanding the Vex. Hence, why they were after him. More than likely, it was learning blue to use the Vex Network. Much like The Stranger, I believe Osiris learned how to use the Network, jumped to the future and has learned of the Traveler and Speaker's true nature. Since most thought he was mad, and in "self exile" , his words have been discarded as nonsense. The Trails, could be a way of the Osiris Cult to pull followers into learning the truth. Many of their teachings speak ill of the Speaker. Only time will tell though.