If a patch were available, and you were online and signed in, you would get a prompt when starting the game.
I think the Xbox patches for non-US versions are likely going to be delayed until the add-on is released (about september). Unfortunately, with additional changes being made to the game, it doesn't really make sense to release multiple patches when a great deal of time and effort can be saved by combining the testing and release procedures. In particular, Microsoft has limits on the size and number of patches that can be released for Xbox games.
Divine Divinity was originally called Divinity: Sword of Lies, but the publisher changed the name. D2:ED is a continuation of the story from DD, and much of the plot was summed up in some of the 'history of' series of books and various dialogs (and in the link above).
Beyond Divinity was set after DD, and before D2:ED, but in a different realm (where Damian was exiled by the Divine One).
