That are a bunch of (mostly small) feature requests in bugzilla under the 4.10 milestone. Just some highlights here.

To make the panel more flexible in vertical mode and also horizontal, it will get 2 new properties: number of rows and a deskbar mode. The rows will give more control over multi button plugins like the window buttons and allows packing “small” plugins in columns. Deskbar is a vertical panel with horizontal orientated plugins, this makes the panel much more efficient on large displays.

Work is done in the nick/deskbar branch and Andrzej's Github branch

Completed: 50%
Assignee: Nick, Andrzej
Difficulty: Moderate

There are a couple of plugins in Xfce that handle the session. The panel has the actions plugin, xfce4-session the xfsm-logout-plugin and there is the xfswitch-plugin. Since this is all very generic, it makes sense to put this in a single plugin to avoid confusion for users.

Completed: 100% 81a2d7
Assignee: Nick
Difficulty: Easy

• Tasklist: Add option to disable mouse scrolling (bug #6996).
• Panel: Make compositing settings insensitive instead of hiding them(bug #7862).
• Panel: Add style property to control size of autohide window.
• Panel: Add option to disable struts in the dialog (bug#7202).
• Showdesktop: Allow middle-click to shade windows (bug #7177).
• Tasklist: Make the plugin shrink instead of expand (bug #7389, #7129).