All elected officials of the city holding office at the time the council-manager plan is adopted hereunder shall continue in office until the expiration of their respective terms of office. The mayor and councilmen or aldermen of the city, prior to the time of the effective date for the installation of the council-manager plan, shall have power to provide by ordinance for any details of the orderly transition from the prior form of government to the council-manager plan, not otherwise specified by law.