I've been making my way through the series lately and I've reached the last few episodes of Season 3. A few episodes ago I watched the Two Part episode with the return of Sinclair which is as I understand is his last appearance. So I would imagine the storyline about his destiny and his significance to the Mimbari is over. It certainly seems to have tied up most loose ends, but I still don't quite understand the intrigue they were trying to build back in Season 1. Why did the Mimbari Federation want Babylon 5 to be run by Sinclair? And why did they seem to think he had some specific purpose to them? I know he did have a Mimbari related destiny, but they couldn't have known about that.As far as I could tell the only reason the Grey council seemed interested in him personally was that he was the first human they picked at random from the Battle of the Line. From what Lennier explained in Season 2 the reason the Mimbari surrendered didn't have anything to do with him specifically. I wouldn't normally ask something like this before finishing seeing the show but I would imagine this isn't explained later in the show's episodes but if it is, I guess I would prefer to avoid spoilers.