The WTS is merely one of dozens of cults / high control groups available to people who are mentally and/or emotionally disposed to be abused.
Such groups come and go, but there will always be something, as long as there is a need to fill.
The WTS has shown itself to be more resilient than most groups.
I think its days of growth are gone, though. It will soon begin a slow & gradual decline into (further) irrelevance.
50 or so years from now, JWs will be about as (non) numerous & prominent as, say, Christadelphians or Quakers. An odd historical footnote, and every time they are mentioned, people will say "are they still around?"