What would happen if people did not update their validating resolvers with the new .ORG zone key?
Once the old key is purged, domains in the .ORG zone that were signed would no longer resolve for those people who did not use the new .ORG key. It would not affect people that are not using DNSSEC – they would continue to see the domain name, however they would also not receive any of the security benefits of DNSSEC.
