Never say never. We know damn well that they're saving them for a future plot. Horde won't be able to do much against the Void if they stand scattered and without order. Illidan would see them as agents of the Void without standing with the Alliance. The same is true for the Alliance. Illidan would especially vouch to eliminate the Horde if anything happened to his family.
The Kirin Tor can survive Rommath. They won't heed his pleas, especially if their loved ones die (a list of powerful connections). See Vereesa.