According to the company, WordPress 3.9 is in his last beta and about to be released mid april.
It is recommended to update your WordPress because of many security reasons but also because there is always a list of new features, especially in full versions.
- Live Preview Of Photo Galleries – you will be able to see live gallery previews in the visual editor
- Better Image Editing
- Drag and Drop Images – now you can simply drag and drop images into the visual editor section while you’re writing a post
- Live Theme Previews – now you can see what everything looks like before it goes live
- Live Widget Previews in Theme Customizer – you will be able to see live previews of widgets in the theme customizer
- Audio / Video Playlists – users will be able to create audio/video playlists
- TinyMCE aka Visual Editor Updated
- Improved Add New Theme Screen – a change in the design of new theme screen and also a few new features