I do not believe on sudden exodus at all. Anyone who were in the WT cult through 1970's-1990's would see the BS and walk away knowing that the theology, system of beliefs, and organization is nothing more than man-made invention. Yet, only individuals left. Other stayed behind. While WT is certainly in crisis, I see it as transformation phase to new level of BS to move from American business model of Knorr's era and vision of 1950's to something more global and less American. It is not the same religion I grew up and I left 20 years ago. As a group, JWs really do not care about flip-flopping doctrines, they just want to feel to be part of exclusive pact that would give them some assurance in survival of big "A" or after resurrection.
While it is possible some groups will split, WT survived 1925, 1975, and gen of 1914 fiasco, and will survive all of us. It is a wishful thinking that WT will explode and cave by many who left WT, but this won't happen.