BlackBerry is doing a decent job of keeping legacy BES up to date. Their latest update is going to be BES 5.0.4 MR6 which is coming sometime in the near future. My buddy Piotr at BBNews.pl noticed that BlackBerry posed up the change log documentation for the release which means it is coming shortly. The update has one specific noteworthy feature which is support for the latest Microsoft Office 2013 attachments as opposed to the previous support up to Office 2010.
Check out the documentation PDF here