I dont think the end of the organization will come in any of our life times.
But i doubt that it'll last pass 2100.
Sooner or later, they'll be more people being disfellowshipped/dissassociated as opposed to those who are active.
In my opinion, the WTBS right now is banking on third world countries. Thats where most of the growth is coming from these days.
I have a theory that china will eventually become a "democracy" and this will open the doors to greedy organizations like the WTBS, church of latter day saints and Scientologists.