Earlier, the provisions of section 269 were not applicable to Private Limited Companies and the Appointment of MD was done in the earlier Act and i suppose no term was should be fixed for the appointemnt at that time.
it is clearly given in section 197(2) No Company shall APPOINT OR REAPPOINT any person as its Manging Director, Whole Time Director or Manager for a term exceeding five years at a time.
In that case, in my opinion, you need to do nothing to change the appointment as per new act. IN caseof any change (appointment or reappointment) you need to comply the provisions of the New Act. Other wise he may continue as MD as per his terms of appointment.
It is my opinion, Contrary views are welcome.