It could also be foreshadowing the possible creation of new Heralds? The others broke their oath, but perhaps a new one can be made with a new set? It was implied in WoK that they used to be something besides Heralds, and, I can't quite remember the quote, but Kelek in the prologue was thinking about how Jezrien still looked like the king that he used to be.
EDIT: Slight word change.