The court shall have power at any time, upon proof that any such owner or owners named in such petition who has not been served with process has ceased to be such owner or owners since the filing of such petition, to impanel a jury and ascertain the just compensation to be made for the property (or the damage thereto) which has been owned by the person or persons so ceasing to own the same, and the court may upon any finding or findings of any jury or juries, or at any time during the course of such proceedings enter such order, rule, judgment or decree as the nature of the case may require.