Update: With just 3 days before the Ubuntu 15.04 release, Unity was updated with only one change: the default out of the box menu was set back to global menu.

After getting an option to always show the menus as well as global menu (Appmenu) support for Java Swing applications, yet another menu-related change has landed in Ubuntu 15.04 Vivid Vervet: locally integrated menu (LIM) is now the default menu.

Unity developer +Marco Trevisan is working on some tweaks for Ubuntu 15.04 Vivid Vervet and among them, there's a fix for a three year old bug related to Unity's menus. 

Marco's work involves adding an option to always show the Unity menus (in Unity, the menus are currently displayed on mouseover). Furthermore, this option will work with both the regular Appmenu / global menu, displayed on the top Unity panel, as well as LIM (locally integrated menus), displayed in the application titlebar:

It looks like a new "locally integrated menu" will make it into Unity, starting with version 5.6.0. There's basically no information about the new locally integrated menubar, except for two bug reports which link to some custom Unity, Compiz, Metacity and Light Themes branches so to see "LIM" in action, I've compiled all these branches and here's the result: