Since it’s a replaceable event a client would need to voluntarily publish the past pfp information or a service or client would need to keep track of it locally otherwise you’ll just get the current info.
Discussion
nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s was discussing versioning if I recall correctly for long form notes. Not sure if profile versioning is / will be supported.
