Whatever happens, the Watchtower will spin it as a sign of the final part of the last days.
Meeting attendance will not just go down, but I imagine it will be the old timers who are filling the seats at the Kingdom Hall.
The door-to-door ministry has been the main pillar of JW life, but I think it will evolve. To keep members active in any form of the ministry they will have to continue to dumb down their product. The Watchtower will do this as a cost saving measure and a safeguard from having their members do their own research.