From Exchange Team blog:
We are happy to announce that Exchange 2010 is Code Complete! Our senior leadership team has signed off on the final code, and it has been sent to our early adopters for one final look before its public release. This Release to Manufacturing (RTM) milestone means we are on our way to general availability and the launch at Tech·Ed Europe 2009 (http://www.microsoft.com/europe/teched/) in early November.
Great job guys.