However when conversion rates drop (i.e. most converts are descendants of JWs) the JW population will become more representative of the actual population (i.e. older). That means the death rate will increase and the fertility rate will drop. If this is true that means that even if the current conversion rate/ability to baptize and keep children in is maintained the resulting total growth may be lower than now.
Bohm, since the PEW report states the JW have the lowest retention rate of all religions, then the hypothesis of more children of JWs leaving is accurate, plus adults also leaving or being disfellowshipped. Add into this the encouragement to remain childless and to focus on ministry, plus the discouragement of higher education. I'd say the death rate is not only representative of the total regular population, but even a pretty high % compared to regular population.