The much anticipated new version of BizTalk Server has been Released to Manufacturing and is now available for download from MSDN.
To see the details about this release please see: http://blogs.msdn.com/b/biztalk_server_team_blog/archive/2013/03/21/biztalk-server-2013-is-now-rtm.aspx
There has also been changes in the Licensing model for BizTalk Server 2013, it has now moved from Processor to Core Licensing: BizTalk Server 2013 Licensing Datasheet and FAQ