Today Microsoft announced BizTalk Server 2013 is now Released to Manufacturing (RTM).
The software is now available for download through MSDN in English only. Just do a search for "BizTalk 2013" to find it.
This release brings new adapters, better Azure integration, enhanced SharePoint integration, support for SQL and Visual Studios 2012, and more.
Look for the RTM release as a VM role available on Windows Azure soon as well as the release of the EDI PaaS offering known as BizTalk Services.
Enjoy!