I believe from what I have read so far that they may be due possibly for release sometime in June/July 2008. I hope so, as I was looking at upgrading to a 3870x2 soon but may now wait until then. Hopefully some reviews may start to filter through and even eventually some estimates on prices. The small things that I've heard about them so far do make them sound goooood!
I do have a horrible feeling though that they may be too expensive for me as I am pushing the boat out even thinking about getting a 3870x2. But you never know, ATI still seem to like looking after the wallets of it's customers whilst providing them with excellent performance.