I don't think being able to migrate your account addresses the rugpull concern. The rugpull scenario is that one day, in five years or so, bsky.app drops all AT Protocol support and transforms into a Twitter-like centralized social media website. The problem isn't that the account will stop "existing" but that Bluesky users will stop seeing it. The average non-techie Bluesky user who doesn't know about the AT Protocol won't even notice the change, except that, from their perspective, a tiny percentage of nerdy users have stopped posting. For you, "migrating" your account away is effectively just deleting it from the now-centralized Bluesky and willfully decreasing your audience by 100-fold or more.

The problem is a social not a technical one. It doesn't matter how good AT Protocol is at account migration. The vast majority of AT Protocol users think of themselves as Bluesky users and don't even know what the AT Protocol is. If the official Bluesky clients move away from the AT Protocol, the majority of users are moving with Bluesky.

For all the UX concerns people have with Mastodon/ActivityPub, at least they make it obvious that different users are hosted on different instances, and no one instance has more to gain than it does to lose by defederating.