It took a while, but here it is... BizTalk Server 2013 is now in RTM (Manufacturing)! as of now you can download BizTalk 2013 from MSDN, and it will be available for purchase in April.

Besides all kinds of new features, the new version of BizTalk also brings us a whole new licensing model. At least it is new in terms of BizTalk pricings... it will be a per-core licensing model, just like the SQL Server licensing.

A more detailed info can be found on my companies blog post.
the official announcement of the BizTalk team, can be found in this post on their blog.