So if Samuel L. Jackson doesn’t want to do any other Saw movies after this, he won’t have to, because hypothetically the next Book of Saw will see another disciple’s turn in this mad world.
Which, in turn, means a new story and fresh characters being employed in each film, which will naturally mean new and more demented traps to come in the future.
Another interesting possibility that springs from an anthology perspective is that it also plays the American Horror Story card of enticing high end talent to participate in one off entries.