This is a Minimus-type question.
But what would it take for the Society to mainstream, perhaps like the Adventists? My top five in order would be:
1. disfellowshipping never cuts family ties and is restricted to willful acts contrary to christian ethics.
2. blood transfussion become a matter of personal choice, no disfellowshipping.
3. children are permitted to attend school functions so they don't feel so alone, particularly around the holidays
4. service time is no longer kept and not a requirement for attaining some position in the congregation
5. it accepts itself as part of the world, opens its books, turns in pedaphiles, and accepts the consequences.
If this came about I would imagine that 50% of the faithful will leave or just coast along, literature "sales" will drop accordingly and lawsuits would need to be settled. Without the need for expanding factories, the WTS could sell off some property to settle lawsuits and develop a retirement fund for all its full-time workers.
And yeah, pigs will fly!