The KDE Project just announced the first RC release of the new 4.12 version of Applications and the KDE Development Platform.Just like the previous KDE development releases in the new branch, it does not include Plasma Workspaces since it was frozen for new features in 4.11.x
“With the large number of changes, the 4.12 releases need a thorough testing in order to maintain and improve the quality and user experience. Actual users are critical to maintaining high KDE quality, because developers simply cannot test every possible configuration. We're counting on you to help find bugs early so they can be squashed before the final release” reads the official announcement.
More details about this release can be found in official announcement. Also, you can download the latest KDE 4.12 sources right now from Softpedia.
Remember that this is a development version and it should NOT be installed on production machines. It is intended for testing purposes only.