WordPress 3.9.1  is released after WordPress 3.9 is being downloaded more than 9 million times!
This maintenance release fixes 34 bugs in 3.9, including numerous fixes for multisite networks, customizing widgets while previewing themes, and the updated visual editor. We’ve also made some improvements to the new audio/video playlists feature and made some adjustments to improve performance. For a full list of changes, consult the list of tickets  and the changelog .
Also WordPress 4.0 is targeted on the week of 25th August 2014. It may sound like a big jump in version number, but the release size will be roughly about the same as 3.7 -> 3.8, 3.8 -> 3.9, etc, on the same 4-month cycle!
Download: WordPress 3.9.1