If you're an existing AppEngine standard user/customer, it's pretty likely that that means you will not be able to take advantage of PostgreSQL, as the new runtime does NOT give you access to a ton of their existing services that you are probably already using (such as datastore.)
Hi optimusclimb -- just want to make clear that using Cloud SQL to connect to PostgreSQL should work using Python 3.7 on the App Engine standard environment. Your earlier comment accurately pointed out a gap in our docs. We're going to address that -- thank you.
If you try Cloud SQL and find that it doesn't work with PostgreSQL on this new runtime, that's a bug and we need to fix it.
I think what he's saying is you're currently using Python 2.7 on Standard and using existing built-in services like task queue, memcache, ndb, etc then switching to the new Python 3.7 runtime (to be able to connect to Postgres) runtime really isn't possible since there aren't non-rewrite solutions for those missing pieces.