In the event of redistricting which changes the number of congressional districts in the state, the members of the commission as constituted at the time of redistricting shall continue to be members of the commission until the first day of July following the expiration of four months after such redistricting becomes effective. Except for the chairperson on such date, the terms of all members of the commission shall expire. During the four months immediately preceding such termination of office, new commissioners shall be elected and appointed from the newly constituted congressional districts in the same manner which is provided in this act for election and appointment of commissioners. The terms of elected and appointed members first chosen from such newly constituted districts shall be staggered on the basis of the number of such districts and their successors shall be elected and appointed in such manner and for such terms as provided in this act.