With the removal of libkipi-15.08.3, the minimal use flag required by slot 5 libkipi versions for peaceful coexistence with slot 4 versions has become impossible. This causes an unresolvable blocker for me.
This was fixed already: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=58987ca38df1689f4ec0e32723ef536570e9deac Might need to wait a couple hours depending on your mirror to re-sync.