There is another in the works. Current Members of the first two Clubs (Warrior's Club and Dial Me) will have preference. But there is little incentive for them to join the new one as they already have the perks that go along with Club Membership. Just watch the Churchill Downs website for the announcement of the new Club.
I just went to the website. They say that if you are interested you should express your interest in the 2017 Club by sending an email to
RacingClub@KyDerby.com