With most development efforts being focused upon KDE Frameworks 5 and Workspaces 2, only the applications to the KDE desktop are seeing much activity for KDE 4.12. KDE 4.12 will be released in mid-December with its few new features.
Since the first KDE 4.12 Beta earlier in November, there's been the feature/API/dependency freezes so the second beta and now third aren't too exciting. Going into KDE 4.12 Beta 3 are just bug-fixes and other polishing.
For those wanting more information on KDE 4.12 Beta 3, check out the information at dot.kde.org. Meanwhile stay tuned for the final release in December along with the forthcoming preview of the next-generation KDE stack.