To add IPv6 support for Cloud SQL, our Product teams need to fully support IPv6 in Andromeda (the building block for all of Google Cloud’s network) given that any packet sent or received by a VM was sent or received by Andromeda.
Adding support for IPv6 in Andromeda is still a work in progress, but there has not been any ETA on it yet.
The Software Engineering team does seek to support IPv6 addresses on Cloud, and once IPv6 is fully supported by Andromeda, the Cloud SQL team can begin the tests to add support for it.