They are due to use the economic troubles as a sign that the end is imminent. Once the dollar starts becoming worthless, they are going to assume that Jehovah is about to step in and usher them into the New Dark Ages, where the dollar will be unnecessary. Never mind that this is not the first time we have seen a collapse in the dominant world power--just that they will spin it to mean that the last world power is going down, and that Armageddon is nigh.
Then, once Agenda 21 becomes reality, the witlesses will claim that this is "the eighth power" that reigns a very short time. It will always be taken to mean that the end is imminent. Not that they will wake up to the fact that mass human enslavement, not liberation, is all Agenda 21 will bring. (And mass human enslavement is also Jehovah's agenda.)