What is the eta for Plasma 5.7? I assume it’s pretty close given that it’s in the arch repos already?
QT 5.7 is in testing.
Plasma 5.7 is in unstable
However, QT 5.7 breaks the unified look for qt apps on GTK environments, the Manjaro team is working on this.
https://forum.manjaro.org/t/testing-update-2016-07-06-haskell-python-pamac-firefox-lumina-gnome-session/5380/1
I use the unstable repository and currently upgrading to Plasma 5.7 as I type this.
Your going to need to do the following to workaround the QT 5.7 theme issue:
Install qt5-styleplugins and qt5ct
Set environment variable in /etc/environment QT_QPA_PLATFORMTHEME=qt5ct
Restart the system
Start qt5ct and select gtk2