Hi Steve,
By "Release" are you asking how we perform these updates in DSpace releases themselves? Or are you talking about strategies for doing this in your own site (like pushing these changes from dev to production locally)? I'm going to guess the latter.
Not sure if it helps here, but the DSpace Upgrade process somewhat helps with this. When running "ant update" to redeploy the backend, you'd automatically update the copy of submission-forms.xml and/or any metadata schema XML files (in [dspace]/config/registries/). Part of that "ant" step is to copy over config updates.
After that, you could run "./dspace registry-loader -metadata [full-path-to-metadata-schema.xml]" to tell DSpace to update it's database based on updates to that registry. This command is triggered (for each metadata schema XML) automatically whenever other database updates occur (via a Flyway callback). But , it can also be run manually via the commandline.
Hopefully those give you some clues. If not, let us know if I misunderstood the question.
Tim