Hi @fakky ,
Welcome to Google Cloud Community!
First of all, there is no official release date yet for PostgreSQL 17 support in Google Cloud SQL. But, based on the [support date for PostgreSQL 16](Database versions and version policies | Cloud SQL for PostgreSQL | Google Cloud and pattern, it will probably be by the end of the second quarter of 2025.
Regarding your question with the upgrade. You cannot directly upgrade to the latest PostgreSQL version based on the known limitation for major version upgrade:
“If you’re using PostgreSQL versions 9.6, 10, 11, or 12, then version 3.4.0 of the PostGIS extension isn’t supported. Therefore, to perform an in-place major version upgrade to PostgreSQL 16, you must first upgrade to an intermediate version of PostgreSQL (versions 13, 14, or 15).”
So, you need to upgrade first to one of the middle versions (13, 14, or 15) before upgrading to 16. Here is the documentation guide for upgrading your PostgreSQL.
Also, you may check this official Cloud SQL for PostgreSQL release notes for any updates.
I hope the above information is helpful.