As announced by WoW game director Ion Hazzikostas in a new episode of the WoWCast, the new optional UI feature is coming as part of WoW's 11.1.7 update.

You can move it around and minimize it into a tiny icon on the screen. One UI 7 builds on this by grouping minimized windows and adding an "Open All" button. It does two things to keep things neat.

Microsoft is currently testing new Xbox Game Hub pages that would provide players with more information but also put their games an extra button press away.