It has been officially confirmed this morning for those in Australia on the 335i coupe with September production for 2009 model year. While we do not have confirmation for the US as of yet we hope to see a release on it soon (though we do not anticipate it). It will eventually happen as our sources have indicated, we are just feeling the US may take some time to make official announcements for this coming fall.
The Australian guide can be seen here
EDIT: For more information on the premise of the BMW DCT system as currently in the //M models you can find the March press release here which covers the system exhaustively.
The 3 series will have essentially the same transmission but with changes in the software as compared to the //M system.
BMW Australia via E90Post.com