We don’t usually see any updates on rendering features (among others) until they are good enough to show, meaning we don’t see any news until it has been merged to . This is one of those features that can’t be partially implemented, so it makes sense for them to wait until it’s fully functional.
A couple of examples: planar reflections, SSR for translucency, DFAO, procedural foliage, etc, were all either within days of being added to , or already in it before they posted any info publicly (aside from trello).