Why would it? They can still lock everything down and few Bluesky users will even notice. This is similar to what Twitter did, or what Google Chat did, etc. Compare this to other federation platforms where a server that locks itself down loses access to a huge chunk of the network, once the other servers reciprocate.
Since migrating your personal data was a thing they thought about since day one, migrating to another network than the current one would be way easier than any centralized service and also easier than ActivityPub.
Seems there is one piece of the puzzle missing yet ("AppViews") in ATProto to be able to run completely independent, but seems they're currently working on getting that in place now.
Yeah? I don't remember being able to migrate from/to Twitter and taking followers/following etc with you without having to ask/request others to do something too.
Oh yes, and they are the only ones owning and developing AT Protocol, which makes it much more a currently-open-sourced protocol rather than a standard that is jointly developed by the industry.