The package.unmask/.kde-4.6 directory in the KDE overlay is (apparently) missing a symlink to kdepim-4.6. Without the symlink, trying to unmask and emerge @kde:4.6 is failing because the various kdepim set components have not been unmasked. Adding the symlink and running regenerate-files fixes the issue and @kde can be emerged without complaint.
which is the desired behaviour, as kde 4.6 works with either kdepim 4.6beta or with kdepim 4.4.10. it is also documented http://www.gentoo.org/proj/en/desktop/kde/kde4-guide.xml#kdepim
