Is it ok to use “xfce4-devel-meta 4.15”? Will it messed with my desktop? Somebody tested it?
It does not seem to be in the Manjaro repos, so it will have not been tested. It is available via the AUR, at your own risk.
More info on repos and the AUR:
Personally, I rather wonder how safe it will be to update from 4.14 to 4.16.
My KDE experience was bad.
do a snapshot and test it fearless
Is not there yet. Test it on a VM. You will not like an unstable main system.
I tried it on a VM.
I downloaded the sources from Index of /xfce/4.16pre2/src/, compiled and installed over the existent Xfce 4.14, I see that not messed with the load of Xfce, but I will wait till December or January for the final release to use it in the main system.
The package meta-package "xfce4-devel-meta 4.15” is not ready yet.