I've maintained for a long time that if the WTBS collapsed a significant number of JW's would just go find somebody else to tell them how to live. They would be low-hanging fruit for a charismatic leader to harvest.
When you think about religions like Mormonism and Scientology, you have very recent creations
Scientology yes, Mormonism no, depending on what time frame you use. The Mormons predate the Watchtower.
The Watchtower, Christian Science, and a slew of Adventist groups sprang up in the mid-to-late1800's, all of them with their roots in the Millerite movement of the 1840's. Miller (and later his imitators) left behind a lot of broken predictions of the End, and a good number of disappointed followers. None of that stopped people from joining other, similar, religions. That might be a useful example of what happens when a religion collapses.