[_emacsomancer_]

It's perhaps less likely for Twitter than any one given Fediverse server/Mastodon instance. But the impact on the whole ecosystem is very different too. A single Fediverse instance shutting down could be annoying/sad, but it would only affect a subset of users, and those users could still, if need be, create a new account on another instance. Twitter shutting down closes everything for everyone.

[WorldMaker]

Relatedly, Twitter isn't going to throw a bake sale to try to stop from shutting down, it will get devoured as quickly as it files Chapter 7 or Chapter 11 and debt holders descend like vultures.

Most Mastodon instances are community run, and when they hit some rough straits in paying for their hosting some of them will have a (metaphorical) bake sale encouraging users to contribute to the hosting fund Patreon or will ask around if someone wants to take over the admin hot seat for a while.

For those concerned about the longevity of specific instances that's generally the answer: ask the community how the admin pays for things, look for their Patreon, consider chipping in what you can each month.