“Today KDE releases a beta release of the new version of Plasma 5.4.

This release of Plasma brings many nice touches for our users such as much improved high DPI support, KRunner auto-completion and many new beautiful Breeze icons. It also lays the ground for the future with a tech preview of Wayland session available. We're shipping a few new components such as an Audio Volume Plasma Widget, monitor calibration tool and the User Manager tool comes out beta.”

I found 5.3 to be already "migration worthy", but 5.4 is looking really really great ;)

https://dot.kde.org/2015/08/11/plasma-54-beta-adds-shine 

Full changelog