I am concerned about the McDojo version of the "black belt club", which is usually a way to pre-sell black belt courses and get extra money. I was just reading a spam email that came from an American Kenpo teacher that said that when you sigh up for his course you will be given all the requirements and know the exact day you will get your black belt.
But there are some good schools who offer regular classes, where they know most people will be there for "fun and fitness" and be there only 3 months on average and that 98% will drop out with out ever making Shodan. And that's ok, as long as the teacher is honest about things. These types of schools will have to offer extra training in order to make it possible for those serious students to make thier goal. If that means having a "black belt club" that meets for an extra hour after regular class or for intensive weekend training then that's ok.