I think the trend of losing members will be more of an exponential rate than linear. For many of the reasons discussed here all coming together.
As I understand is the Watchtower has three sources of income. As Publishing Company - that is seems they make more money from the congregations than anyone. as a Cult keeping the herd in blinders and controlling what they think and away from truth - but give them free money. As free slave labor to work for the Publishing Company and very hard free slave labor for the Cult to get more members - judged on time slips?
Really? I always thought God would know. Why does God need with time slips? (Reminds me of one of the early Star Trek movies "what DOES God need with a starship")
The real change is societal change around them. It's not the 1930's any more - you can no longer manage the herd the way they used to. The rate of information is exponential. In 1930 you could never learn of the WT history - now you can't avoid it. Their ability to control people is constantly slipping from them.
A long history of forbidding secondary education - so you don't get smart enough to think for yourself and leave. Just doesn't work in modern day society.
The increasing drop in membership will hurt them financially in increasing way. But they do have enough real estate to sell off for years.
I do like the aging-out statements. As more are leaving, or passing away, it will continue to break the generational chain in a snowball way. Something they have counted on for growth for 100 years. No work - the herd will multiply. No longer a projected growth and they know it.
Religion as a whole has been on a decline for years, and they will probably get hit hardest.
Overall, they have to know due to probably a dozen discrete factors, the numbers will drop precipitously. It all hits the life blood of the WT - their income/money.
I think they should move the head quarters to a 3rd world country. Where it is still the 1930's - where they thrive with no information available except what the WT tells them to believe. No secondary education either. Of course they have no money to leach from like the US.