Ok, so this was available for a few days now but I’m reporting it here now after having used it for the past several days. If you’re using either Kubuntu 16.04 “Xenial” or 16.10 “Yakkety” you can now upgrade Plasma to version 5.8 via the Kubuntu Backports PPA:
sudo add-apt-repository ppa:kubuntu-ppa/backports
sudo apt-get update
sudo apt-get upgrade
A huge thanks to the Kubuntu guys and all the KDE developers for continuing to do amazing work in creating such an excellent desktop environment which truly defines the cutting edge!