Work on KDE Plasma 5.6 will start soon, and the repository freeze will be on February 18, 2016.
Then, the first Beta build will be available to testers worldwide on March 3, along with the feature freeze, two days after the release of the last KDE Plasma 5.5 maintenance. The final build of KDE Plasma 5.6 will see the light of day on March 22, 2016, and it will be followed closely by the first bugfix release, KDE Plasma 5.6.1, on March 29. As expected, the KDE Plasma 5.6 series will have a total of five maintenance releases.