Right now, we display a warning about image stability in rolling release images unconditionally, because the current branch is never an LTS release. However, adding that bit to stream branches and reverting them when they reach LTS status doesn't sound like a sensible idea.
Since there's build_type in version.json, we could display that banner if the build type is not release. That will make it easy to mark an image as production-ready or not by using a different --build-type.