Edit: Due to the fact that this article is old, the installation instructions may not work anymore. In order to successfully install the latest version of KDE Plasma, please access the KDE tag and open the latest article (the one on top).
The latest installation instructions for KDE Plasma
Hello Linux Geeksters. As you may know, KDE Plasma 5 comes with many important apps ported in Qt5, the new Kicker Menu, a new default theme called Breeze and new wallpapers, new monochrome icons, support for hardware acceleration via OpenGL and OpenGL ES, an updated KDM (KDE display manager) and an enhanced lockscreen, among other changes implemented.
The latest version available is KDE 5.3, which has been released yesterday.
Kubuntu 15.04 (which will be released tomorrow) uses KDE 5.2 as default, but if you want KDE 5.3 on your system, you can install it via PPA:
$ sudo add-apt-repository ppa:kubuntu-ppa/backports
$ sudo apt-get update
$ sudo apt-get dist-upgrade
Optional, to reverse the changes, do:
$ sudo apt-get install ppa-purge
$ sudo ppa-purge ppa:kubuntu-ppa/backports