I'm not sure what either of you are talking about here. Modules are all packaged up in Ansible Content Collections these days. One of them, ansible.builtin, is included in Ansible Core. If you're using automation execution environments, the container image might or might not include additional Ansible Content Collections as part of the Ansible "installation" in the image. That's true whether Red Hat built the image, or you built the image (although in the latter case, what's in there is up to you).
And you can always use requirements.yml in your project to get more third-party Ansible Content Collections from a number of sources (not just Ansible Galaxy) downloaded into your project directory by using the ansible-galaxy command. The whole project directory is bind mounted into the container even if you're using an execution environment, so those collections would be available just like the playbook. I think that automation controller automatically runs ansible-galaxy on your requirements.yml when you launch a job. Otherwise, I suppose you could periodically run it on your project's Git repo and check in the updates.
I wouldn't expect that Ansible Content Collections "come to an end in AAP" in any way.
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