As you may know, KaOS is an open-source Linux system built from scratch (not based on an existing Linux system) that uses KDE Plasma desktop by default. Also, it is a rolling release system, like Arch Linux, Manjaro or Kali Linux 2.0.
The latest version available is KaOS 2015.8, which has been recently released, using the newest KDE Plasma desktop available and uses Wayland as default.
The official announcement:
“This ISO brings a long list of wonderful improvements to all of KDE. Biggest part undoubtedly is the first time to have the option to run Plasma 5 in a Wayland session. It still is in an early stage, so kwin_x11 is, of course, the default still. As for the desktop, this ISO brings all the latest of Plasma 5 (Frameworks 5.13.0, Plasma 5.4RC) and KDE Applications 15.07.90. All build on Qt 5.5.0. Plasma-volume-control is now part of the Plasma 5 group, renamed to Plasma-pa (for sound plasmoid),”