Given there will be a number of deaths each year plus people moving away (including younger folks going away to University) there will always be some natural churn in season ticket holders.
http://www.theargus.co.uk/sport/albion/16092535.Albion_reveal_96_per_cent_season_ticket_renewals/
Means only "up to 800 season tickets" are up for grabs to those on the waiting list!