From the outside looking in, as a non-JW, I can understand why many ex-JWs are not convinced the downfall will happen soon, if at all.
Consider this, however: the Watchtower no longer controls the message. In fact, the message (from the outside world) controls them. Why else would they become so reactive? Why else would the GB make those ridiculous broadcasts, which show them on the defensive?
Skedaddle is spot on, I think.
Moore's law was brought up. A good parallel might be the industrial revolution. Look the effects of it, in the span of a century, compared to the slow technological progress in the centuries leading up to it. The same thing is now happening with the information age: look at how much the 'borg' has changed in the past decade, compared to the 100 years prior. Who would've thought, back in...1982, that the GB would become money-begging tele-evangalists, fleecing money from their churches (halls), being grilled in front of judges for child abuse, cutting their once reknown publishing empire, closing branches, cutting the Bethel workers....all within a decade, and all coinciding with the seemingly exponential spread of information technology.
You might say, "well, the shakers & amish are still around, and so the JWs will still continue." To which I say, "agreed." Sure, they might endure in small, isolated pockets here and there. They might become a splintered fringe-cult. But even THAT outcome would be desirable IMO. They might not go extinct, but they'd certainly end up on the endangered species list.