Ended up having kde 4.x (plasma 4) instead of Plasma 5.4 from Ubuntun 14.04

I was using Unity on Ubuntu 14.04 and was giving me trouble after going dual monitors, so decided to give KDE a try. So I installed KDE by following the commands below found here hoping that I'll get Plasma 5.

sudo apt-add-repository ppa:kubuntu-ppa/backportssudo apt-get updatesudo apt-get install plasma-desktop

I really like KDE but I have ended up with KDE Plasma 4.x as the --version says below:

$ plasma-desktop -versionQt: 4.8.6KDE Development Platform: 4.14.2Plasma Desktop Shell: 4.11.11

And also here's how IKnfocenter looks:

How do I get Plasma 5.4 (NOT 5.3 as it's unstable from what I read)?