An internal test ISO is up, build on [kde-next], so it includes Qt 5.11RC2 & Plasma 5.13beta.
This ISO also moves to kernel 4.16, has a fix for grub failures on BIOS systems using XFS partitioning.
Calamares is not updated yet, so it still shows settings for the April ISO. Also not included yet is nvidia 390xx (since it needs changes in Calamares to work). It is a minimal ISO, virtually no apps.
So anyone willing to help test, get this ISO and just use it in live mode, no use to install yet.