I think there is a "straw that breaks the camel's back" factor. I think all JW's are carrying at least some doubts and have noticed their fair share of discrepancy.
It is just a matter of time before many of them have simply had enough. This may be when something bad happens to them or to someone else at the hands of the elders or whatever the case may be.
I just believe that there are always cracks in the foundation before this happens. Otherwise they would go along the whole "Jehovah is just allowing this to happen for some reason" routine as many "faithful" do.
I will add this: This new light business is creating cracks for many people. It also reminds people of their old doubts (generation change etc). They aren't leaving immediately, but it piles more on the "camel's back" for when the big "straw" comes down the line or they simply can't take it anymore.
Sites like this help solidify the "break" once it happens. Jwfacts was priceless for me. This site gave me a place to vent and realize how many people are in the same boat.