In a word, no, however this is probably not a good example scenario.
9/11 for example, certainly forced some people back, (my cousin who was DF for 8 years and a coke head at the time was one of them). An event of great significance, but not catastrophic to humanity, one such as 9/11 or worse, would probably force those who are not convinced 100% JW is not the "truth", to go back. If you look at some older threads here from 2001, there were some here who did exactly that.
I am not one of those people.
d4g