I am curious if the servers in OPs post can de-federate and survive.
If the majority of the fediverse refuses to federate with Meta then this won't be a problem, because people on Meta's instance will never get used to interacting with people outside of it. And there will be no need for small instances to comply with Meta's demands in order to federate with them, because they won't be in a disadvantageous position if they don't.
If they don't give a shit about the fediverse why do they want to join it? Only Facebook can win from this.