The news release says that a la carte classes will still be available as well as a subscription and that previously purchased classes will be available always. So really, the only difference sounds like you will now be able to by a subscription to the entire site instead of just one class at a time.
They also mention other sites that offer subscriptions at $4.95/month and that Comcast has studied the marketplace to come to the conclusion that most consumers would prefer the subscription, so perhaps it won't be that expensive because they have to compete?
Watson