That blog post is *really* light on details. Maybe they assume readers will already know what to expect?

This page appears to be the official list of everything that's coming with 6.8 next week: https://community.kde.org/Plasma/Plasma_6

Things that stood out to me include removal of X11 as a default option at login, triple buffering enabled for Nvidia, Remote Desktop improvements including 2-way clipboard, improvements to screen recording including recording audio and better screen casting performance.

And finally "Shadows and rounded corners for Steam". Steam has always been visually quirky to say the least, so I'm intrigued to find out if this will be an improvement or not.