Kubuntu 15.04 Will Be Based On KDE5
jones_supa writes Kubuntu Vivid is the development name for what will be released in April next year as Kubuntu 15.04. The exciting news is that following some discussion and some wavering, the Kubuntu team will be switching to Plasma 5 by default. They claim that it has shown itself as a solid and reliable platform and it's time to show it off to the world. There are some bits which are missing from Plasma 5 which are planned to be filled in over the next six months. As another technical detail, Debian git is now used to store the packaging in a Kubuntu branch, so hopefully it will be easier to share updates.
And 4 will remain stable, complete and supported for plenty of time to come. But 5 will never get there unless it is released. So, just like most people should have stuck with 3.x until at least 4.2 and probably a bit later than that, stick to 4.x for now unless you want a rough ride. Then, when 5.x is on par with or better than 4.x was, the distros will switch. FWIW, I expect the transition from 4 to 5 to be a lot smoother than 3 to 4 was.