I think people(people includes me, I tihnk the majority of users are new to this stuff) still don't get that unless a certain instance de-federalizes others en masse, you're still gonna be able to access it's content and contribute from your instance.
Although, in general,I wouldn't be worried. Even if a certain instance is getting big, you are still not subject to the whims of some venture capitalist corp in silicon valley.
I'm aware of beehaw defederating. However, you gotta see how it happened. They were completely transparent about why they did it, and that it's not permanent. Once moderation tools start to get added, we'll probably see re-federation.