Good point Besty made upthread. In the last 20 years the WT have baptised about 5.5 million people. The average publishers in 1992 was about 4.5 million, average publishers today is about 7 million. That means around three million publishers have left, died, been d'f'd or faded in 20 years.
JW membership has an extremely high turnover. It seems to me there is a demographic 'hollowing' out now. The congregations are full of old people, mentally ill people and single sisters. It seems like the teenage boys disappear but their sisters stay in. Strange really, since JWism reward system is inadequate for women.
Doctrinally to survive, they don't need to do anything. They lost any remaining intellectual coherence with the 1995 generation change. The further we get away from 1914, the more the 'last days' concept plausibility is stretched, but that doesn't really hurt them. People join for the paradise and stay due to emotional blackmail.