You can download the sources for KDE Plasma can be downloaded from softpedia
The KDE developers have announced that the final version of the new Plasma 5 desktop is finally complete and that it integrates a huge number of improvements.KDE Plasma 5 has been in the works for three years and a lot of effort has been put into this project. It was about time to change the old desktop shell that has been used until now, and the new version looks a lot better and much more modern. It's likely that not all users will like it, especially because there is always resistance to change inside the Linux community.
Similar problems were encountered by the GNOME developers when they switched to the 3.x branch and with Ubuntu when it adopted the new Unity.
“The UI has been tidied up, there is a new Breeze artwork theme starting to take off and high-DPI support has been added. The main design of the desktop and workflows in it have not been altered, we know you like your desktop and have no desire to change it. There is not enough polish in this release to make it mainstream yet, this is only for enthusiasts and people who want to help debug for now.”
“Many distributions have packages to install or test images to try out although this 5.0 release should not be the default option yet. Plasma 5 is built using Qt 5 and Frameworks 5 and is due to have new releases on a three monthly cycle,” note the developers in the announcement.
This is not just a simple upgrade or just another version in a long line of releases. The differences are pretty big and they can be clearly observed because the UI is one of the major features that got changed. For example, a new theme called Breeze (high-contrast, flat theme for the workspace) has been implemented, simpler and more monochromatic graphics assets and typography-centered layouts have been added, and the "converged Plasma shell" that loads up the desktop in Plasma 5.0 can be extended with other user experiences.
Also, users will notice the improved performance of the desktop. This is because the KDE Plasma 5 user interfaces are are rendered on top of an OpenGL or OpenGL ES, taking some of the strain from the processor and using the GPU for a change.
The application launchers have also been improved, the notification area has been enhanced considerably, and high-density (high-DPI) displays are now supported by KDE. To top it all off, a new lock screen has been added, which should make all users very happy.
The new KDE Plasma 5 is sure to arrive in some of the repositories very soon (if it hasn't already). If you don't have it in the repository, you can download the KDE Plasma 5 source from Softpedia and compile it yourself.