I think that if Microsoft ever does decide to support this extension there'll be a patch for all supported versions including via ESU - just like all supported relevant MS products got a TLS 1.2 patch, even the embedded Windows XP (POSReady 2009) got a TLS 1.2 patch.
Besides, since XP doesn't install IPv6 support by default (and these people never update), we should ditch IPv6 too?
No one wants to be bound by 20 year old never updated installs of ancient OSs, so let's not.