There was more that I read. I cannot remember the details, but some have found "???" points in the game like ffxi, and others believe certain currency acquired during leves could also be traded to do HNMs, etc. As for quest line endgame, that has been kept very secret.
I do think Faction Leves may have high value in endgame. Maybe some requiring high amounts of Faction Points to obtain, that would be cool.
I think they want to keep quiet about the endgame. That's one thing that usually isn't really broadcasted for MMOs. I don't want to know all about it anyway, I would rather get to endgame and be surprised.