https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=99f3812a0073527dbe3bccd24e75b1810dc92126 This commit removed the following line: !minimal? ( $(add_kdeapps_dep kdebase-runtime-meta '' 16.04.3) ) So after rebuilding kdecore-meta because of the changed IUSE the following `emerge --depclean` wants zu removed kdebase-runtime-meta and several other rather important looking packages like 'kstart', 'kdebase-menu' or 'kdesu'. That looks like only the "!minimal? (" should have been deleted, not the complete line...
kdebase-runtime packages are from KDE 4 and majority of them are not useful when using KDE Plasma 5. kde-apps/kstart:4 provides /usr/bin/kstart, while kde-plasma/kde-cli-tools:5 provides /usr/bin/kstart5. kde-apps/kdesu:4 provides /usr/bin/kdesu, while kde-plasma/kde-cli-tools:5 provides /usr/bin/kdesu5. This "minimal" USE flag was already absent in kde-apps/kdecore-meta-16.12.*. I think that KDE team is planning masking and later deletion of majority of these packages.