The terms of all other officers in office at the time this Charter takes effect, in addition to the mayor and council, and that of all employees of the city at the time this Charter shall take effect, may continue for the term for which said officers are elected or appointed, and for the period for which said employees are employed. Provided: that the provisions of this Charter as to salaries of mayor and councilmen shall not take effect until the first Monday in January, 1931.