They are doing this as so people can buy them as Christmas presents.
The announcement did state that the ticket is based on a 9 team Championship, which suggests (but does not confirm) they will change them if the structure changes.
I do notice though that it covers 8 league, 2 BSN & 1 KO Cup match, so IF 3 teams joined the Championship you could make the ticket valid for 11 league matches, or for any 11 of the possibly 14 or 15 matches. They could also sell a top up to the season ticket to cover and extra 4 or so matches.
Nothing about the situation is ideal, but I don't blame any promoter for trying to catch Christmas.