For future people reading this post. At HF20 the numbers have changed to :
If SBD supply is less than 9% of the entire STEEM supply, the blockchain prints 100% SBD.
If SBD supply is more than 10% of the entire STEEM supply, the blockchain stops printing SBD entirely
If SBD supply is between 9% and 10%, the blockchain prints SBD according to this formula: 100% * ( 10 - debt), where "debt" is the above percentage between 9% and 10%.