It's definitely possible Meta could try to warp the Fediverse so that it kills all instances other than their own.
This is my primary concern; if smaller instances say "we will block them on sight and anyone who federates with them as traitors" then it's a matter of getting the largest instances to go along with it and suddenly you've blocked a large chunk of users due to the fracture of smaller ones trying to defederate their way out of the problem and into a different issue.
I think @JakeBacon has a reasonable take, there are some upsides, and some downsides. I don't think there is anything that is gained by pre-emptively doing anything though. If they run their own instance, see what it does and then decide accordingly.
Scopique