Unfortunately there is no know release date yet. It is still in the planning and consideration stage.
To be clear, I mentioned this at the OpenFlight User Group meeting as one thing we could work on if enough users showed interest.
So far not enough interest has been shown to put this on our plan. For that reason it will remain in the consideration stage for now.
At IMAGE 2009, Steve mentioned the Low-Level API. Is there a release date/guesstimate?