I'm fairly certain he's dead, as there's a scannable... [spoiler]In the new Tower/Traveler Social Space[/spoiler] ...that talks about the Speaker being gone and finding a new one; it's even made clear he wasn't the first and probably won't be the last. If anything, I think someone will come take his place - perhaps this will happen during/at the end of the first expansion, Curse of Osiris. From what I understand (which please correct me if I'm wrong, I was a little late to the lore side of things) it's going to be about Osiris and I know he disagreed with the Speaker/Vanguard and was exiled/exiled himself. It's possible his beliefs/the reason for his disagreement now line up with what is happening with the traveler and state of humanity.