Except by procedures provided in this Charter, the terms of the elected officials of the City and of officers of the City appointed for a definite term shall not be shortened. The terms of officers of the City may not be extended beyond the period for which any such officer was elected or appointed except that, with the consent of the Council, an elective officer of the City may, after his term has expired, continue to hold office, provisionally, until his successor is elected and has qualified.