They just wait till the old-timers die off.
Blondie's stated it so succinctly. I suspect that the "trouble" caused over the 1975 fiasco is simply a result of the personal impact it had on people's lives at that time. Once the cohort who went through this experience die off, it will not be such a thorn in the Watchtower's side. The religion may alter its emphasis and outlook, but it will survive in one form or another.
Look at the huge disappointment and upheaval in the organization following 1914. They were even able to keeping turning the 1914 doctrine to their ongoing advantage long after the Bible Students of that day were long gone. There is nothing quite so tenacious as believers who need to protect their power and their beliefs.