I'm with Simon's analysis above on this. I think they will just continue to amble along with moderate growth overall - probably already in long term decline in most first world countries but more than offset by the third world. Financially they have ring fenced most of their assets in "independent" holding and service companies ( such as the IBSA and Kingdom Halls Trust ) so they will be safe from any major legal claims.
I guess the main issue they have is the none-arrival of Armageddon - this is a religion with a big sell by date on its ass ( unlike the Mormons , for example. ) . Admittedly they have got away with it since 1879. They have fudged this for decades with recent changes to the "generation doctrine" , for example , which has bought them another 30 years or so but eventually they need to find some kind of new work-around solution - maybe 1914 ultimately will be ditched.