Much as I would love to see the WTBTS implode , I just can't see it happening in the short term. They generated a 3.4% increase last year and I would guess it would be similar this year. Not all of these are poverty stricken third world recruits either - many are the disaffected and lonely in the the first world or immigrants. (I honestly can't remember the last semi-normal person to be baptised who wasn't a born-in.)
The fact is that the WTBTS is a religion (or a pseudo religion) and the normal rules of commercial life (boom / bust / competition / evolution) just don't apply. They have set the bar very high for people to leave while establishing what is something of a broad church so both zealots and apathetic JWs can easily co-exist. The system of shunning critics works well at suppressing any dissent. And the emphasis on evangelism will always bring in some new members as well as the 30% or so of JW children who join up.
A schism or a financial scandal would make something of a difference or a big doctrinal shift (eg letting blood transfusions be a conscience issue). I don't doubt there are brothers in foreign Bethels ( those that the WTBTS haven't closed yet) who are fed up of Brooklyn and that there is a lot of dubious financial dealings below the surface. But in truth even a catastrophic event would have little impact - maybe a 10% decrease (such as happened post'75). And the WTBTS has had 130 years of experience in sweeping problems under the carpet and projecting a positive image. GB members with dodgy personal habits (such as Greenlees and Chitty) are just put out to pasture with a pay-off and a gag. Changes in doctrines are explained as "new light" and given a positive gloss. And the constant brainwashing / conditioning every week , week after week , year after year keeps the drones happy and loyal.