An announcement has not been made by RMT because the deal has not been completed.
Contracts have been issued - but not signed. The winning bidder is still negotiating with the airport. Don't blame RMT for this, it is not they that are dragging their feet.
The problem is, and RMT are aware of this, that as the days and weeks go by, it gets more and more difficult to reform any sort of flying training organisation.
The answer is probably for RMT to give the winner 7 days to complete or lose it.