No, any attempt would be theatre, there's no key ECC-to-lattice key derivation and that's the only thing that would allow events themselves to declare both identities in a way that can't just be "re-declared" post q-day. If you keep nostr what it is (no blockchain time-stamping, etc.) then the only sensible option is for everyone to consider their current identity meaningless (consider their nsec "pre-stolen") and start with a new post-quantum key pair identity, from zero. So all web of trust gone, etc.