No heir. There are probably some ancillary members of the Imperial family, but the emperor has to be Paladine (God), and when the emperor was killed, so was Paladine. The Queen (his assassin) tried to set herself and the Helveki line on the throne, and that triggered the civil war that broke up the empire. Arideen (what is left of the empire in the mountains) is now ruled by a regency council consisting of the High Bishop, the dwarven kingdom (under the mountains), the elven king (from Irine), the Marshal General (military) and a representative of the nobility.