I have been giving this some thought recently. The Watchtower organization certainly does thrive and prosper off of distressing world events. Such events always put new life into the Jehovah’s Witness "end is near" knee-knocking. Distressing events tend to cause active members who might otherwise drift away from the organization to "buckle down" and stay with the organization.
I’m not certain that a severe financial crisis would result in a large influx of JW converts. I think that there is enough information out in the public which will continue to steer people away from the Watchtower. If people begin to pursue religion as a refuge, I believe that they will search out other Christians churches; as they did after 9/11.
After 9/11, I remember that the U.S. saw a spike in church attendance. However, there was no significant increase in the JW membership. 9/11 did more to galvanize and unify the current JW membership than to gain new recruits.
In times of distress, it seems as if the public generally seeks out churches which are involved in the community with charitable activities. The Watchtower organization has never shown any interest in holding a food drive, opening a soup kitchen, or involving itself in other charitable activities except in natural disasters. They really don’t offer anything in comparison to the many "mega" churches.
I do not believe that a major economic crisis would bring about significant growth in the JW organization in the U.S. Other countries may see greater growth; but those here in the U.S. who are inclined to search out religious faith will most likely seek the more mainstream churches.