See https://phabricator.wikimedia.org/T324803, specifically https://phabricator.wikimedia.org/T324803#8515102.
With T324803, it sounds like the JSON output will remain unchanged to be backwards-compatible. To adopt improved paragraph split support on the apps, we'll need to add logic in the wikidiff2 json formatter hook, as well as API / PHP work to pass in a feature flag to opt-in to this logic.
TBD: A new API version number / app-side changes will depend on if the JSON contract needs to change.