It is already happening. The community has contingency plans for each of their communication channels being shut down.
One of the things not in the news is that a 30K user discord server was shut down this week. The community is switching to matrix.org/telegram/signal and has slick on boarding media to funnel users onto these platforms with step by step guides on how to setup accounts and get vetted. The on-boarding process is better documented by these groups than the services themselves.
I've also seen contingency comms plans in opposition groups starting to form should platforms try to cull both sides in an attempt to been seen as playing fair.
What's the end game look like for communities who want to avoid moderation? Things like decentralized immutable message ledgers with vetted in person trust chains becoming an in-demand/enabling technology. If it is mathematically possible to secure comms it will be used.
My personal take? Address the root causes of the disaffected population. Monitoring and reacting is fools game.
I agree with addressing the root causes, but that's a separate issue that Amazon/Apple/Google aren't responsible for.
It seems like this argument boils down to: if the community violating the TOS is organized enough that shutting it down won't stop them, then an exception should be made to the rules.
But do you really think that the world would be better off if they were allowed to continue on Parler? Should nothing be done?