How can I target WordPress 3.8 new interface MP6 with CSS?

When MP6 was a plugin in WordPress 3.6+ it changes the body class of the admin and added an “admin-mp6” class which helps me to style my plugin accordingly.

Now with the latest Alpha of WordPress 3.8 the class was removed. I know since it’s an alpha version the class may come back but I wonder if there are any official “best practices”