If a theme is in development, it is not available publicly ;)
Auberge is not in development. It is done. It is completely new theme. You can download it and use it. And yes, it is the newest theme for now.
And it is not an update of an older theme – theme updates are keeping the theme name, just theme version changes. And I provide updates for all of my themes. For example, recent version of Auberge is 1.2.5 and the next theme update will have version 1.3 and should be released next week or so.