Currently the latest version towards to 3.10 GNOME Series is the unstable 3.9.4 and so far 3.9.4 while fixes around 100 bugs, it didn’t include any major new UI features. That was quite unexpected for Shell that has used us to constant changes in every unstable iteration.
Version 3.9.5 will change all these as it will include some really really cool things that GNOME Devs did. We are talking about the re-designed Aggregate System Menu that will debut in 3.10.
User Menu is gone and is renamed to System Menu and System Menu has been transformed to an aggregate menu that combines lots of staffs (like Power, BlueTooth etc). System Menu will also display items in a dynamic way. For example Airplane Icon will be only visible when is enabled and will also have a -options- submenu when is ON directly from Shell.
Together with those we have some major changes in the way that Shell manipulates popup menus and submenus and therefore Shell Extensions Authors need to make some refactoring to have their extension working in GNOME 3.10.
rest here 
Also: GNOME3 app menu integration