I was specifically talking about push queues, not pub/sub. My comments are also based off of migrating from Python 2.7 vs. 3 where there are additional migrations challenges and GAE limitations.
At least in our experience, it was (or will be...we'll see) easier to migrate off to a generic container based environment.
push queues are available in Google Cloud Tasks. We use them. There's even an article about how to migrate from the appengine ones to the google cloud tasks one: https://cloud.google.com/tasks/docs/migrating
At least in our experience, it was (or will be...we'll see) easier to migrate off to a generic container based environment.