I just hope they don't resort to whitelisting like Google
I don't think anybody wants to keep doing that sort of whitelisting forever. It wouldn't surprise me to soon see an announcement from Google stating that they have decided on a date to end whitelisting and provide AAAA records to everybody. OTOH one way to put an end to whitelisting would be to only apply whitelisting to recursive resolvers that query the authoritative DNS servers over IPv4 and provide AAAA records to all that query over IPv6. Such an approach would be slightly problematic for Google since they don't have IPv6 support on their authoritative DNS servers, they don't have IPv6 support on their recursive resolvers either.
Apart from Google and Facebook is there any major site that uses whitelisting to decide who gets AAAA records? Is there actually any major site that provides AAAA records to all resolvers?