That's an interesting case. I don't think this will happen in correct implementations because either the replaceable event will be treated as the identity key (having implemented 102), or the signing pubkey (having not). Either way the identity of the "current" event won't change, even if the signing key uses rotating attestations.

Key management is definitely a big deal, and in distributed systems rather intimidating. But having worked on SSO in the past, the current situation is risky and holding nostr back. Fixing it won't be easy, but doesn't need to be complicated if we work out the details.