The subzones are being used by staff in some situations, but it's currently not ready for release to the general population. This will be needed to be completed prior to the Empires update if I understand correctly. That puts Dragon tombs and 1.8 ahead in line, so it could still take a little while.
This thread is old, but more light should come down upon it because of what Aikar said earlier today:
Don't mean to be rude, but why should more light come down upon this thread? It seems Aikar is pretty much adding what you suggested but just posted it on another newer thread.
