Bill C-6 creates three new board levels: a five-member land use planning board in the Gwich'in and Sahtu settlement areas; a Mackenzie Valley land and water board, subject to the creation of additional panels which will have up to 17 members, including a five-member permanent regional panel in each of the settlement areas; and an eleven-member environmental impact review board for the entire Mackenzie Valley.
The Mackenzie Valley land and water board will always have at least 5 members at all times. 
They probably will but nothing is certain.  If something happens to one of the five they will need a replacement.