Arising from the TTWG's call on 2023-01-19 and discussion ongoing to create boilerplate for TTWG registries at w3c/ttwg#241, where the idea is to specify that TTWG is the custodian of its own registries, but if TTWG ceases to operate then custodianship would fall back to the Team:

The question arose: shouldn't the Process define a fallback custodian for all W3C Registries if the originally specified custodian is unable to operate? More broadly, if the Registry Definition's process for requesting changes to the Registry is defunct (perhaps the email address has been frozen, etc) what is the default fallback?

It seems unhelpful or impractical for a WG to have to define a process for what happens when the WG no longer exists.