I do agree with what you say, I just don't think they will crumble and fall, not anytime soon anyway.
First of all, I'd like to be very clear. I do not believe that people who have left the organization, aka "apostates" will be the demise of the Watchtower Society in a way that many would assume. First, I think that the role of ex-jws is much more important in regards to the many people that end up not entering the Watchtower system at all. People who may be studying or interested in the faith, but after doing research on the net decide not to.
Also, I am not looking in the short term. I'm thinking more of 30-50 years down the road. Were will the movement be then? I really believe that it fundamentally has to change dramatically. The current structure, or even something that closely resembles it is not prepared to support such a drawn out presence on the world scene. One thing I continue to think of is the youth of the movement. They continue to tell the youth to reach out for positions and privileges they never can receive (gilead, CO, ect), not to mention that usually most of the prestige is given to men. The youth in this organization have nothing realistic that they can reach out and take as their own. This is a huge mistake on the Watchtowers part and shows me that they are not as sophisticated and intelligent as their image may suggest. Smart people plan for the future. Stupid people insist that there will be no future (in this world). I remember a five or so years back the Watchtower published a brochure for their youth that told them all the privileges they could reach out for. It was unrealistic. Gilead for example graduates two classes a year I believe, and those people are usually in their 30's. What the hell kind of goal is that! Work for a decade and a half after high school and maybe you can go to a school with only 100 students. Get real. Nobody reaches out because there is nothing to reach out and take.
Currently the Watchtower is on a path of growing isolation. They are becoming more and more disengaged from the world around them. They control the flow of all information and have restricted what is published on the internet. Rather than engage those who criticize them they ignore the critics and suppress intellectuals from going out and defending the faith on an academic level. They have gone from the time of Russell where debates occurred frequently by those in charge of the articles in the magazines, to complete isolation by the writers of the magazines. We don't even know who writes the articles. They are no names, isolated from any criticism and academic responsibility. It may serve a purpose, but not in the long term.
What I picture is a continued weakening of the Watchtowers power over the average member. Eventually more and more people like Greg Stafford are going to start popping up saying that the group has lost it's way and needs to reform. It is people like him who are really the most dangerous to the Watchtower Society. While many who leave argue that all of the teachings of the JWs are wrong, people like Stafford maintain much of the theological doctrine.
When reformers try to take over a faith it can descent into confusion. This is possible if the WTS allows itself to weaken during the next 30-50 years. The problem is that in order to solidify the movement and push it forward it will have to begin to give up long held taboos and teachings. They can change, and may yet still. But I see nothing that suggests it's on its' way yet. Just more isolationism which amounts to denying the obvious.