The term of elected city assessors shall not expire until a vacancy occurs in the office or upon the completion of the present term for which an assessor is elected. Thereafter the term of such city assessors shall be for the period provided in the charter. The terms of all other city assessors shall continue as provided by charter or as otherwise provided by statute. The term of any city assessor in a county electing in accordance with section 273.052 shall be terminated as provided in section 273.055.