emerge -vt

emerge -1DNuavt --with-bdeps=y @system @world

These are the packages that would be merged, in reverse order:

Calculating dependencies... done!
[nomerge       ] kde-base/kdebase-startkde-4.11.11:4/4.11  USE="wallpapers (-aqua)"
[nomerge       ]  kde-base/kcminit-4.11.11:4/4.11  USE="(-aqua) -debug"
[nomerge       ]   kde-base/kdelibs-4.13.3-r1:4/4.13  USE="3dnow acl alsa bzip2 fam handbook mmx nls opengl (policykit) spell sse sse2 ssl udev udisks upower (-altivec) (-aqua) -debug -doc -jpeg2k -kerberos -lzma -nepomuk -openexr {-test} -zeroconf"
[nomerge       ]    media-libs/phonon-4.7.2 [4.6.0-r1] USE="qt4%* vlc* (-aqua) -debug -designer% -gstreamer* -pulseaudio (-qt5) (-zeitgeist)"
[ebuild  N    ~]     media-libs/phonon-vlc-0.7.2  USE="qt4 -debug (-qt5)" 58 kB
[ebuild  N     ]      media-video/vlc-2.1.2:0/5-7  USE="X a52 alsa avcodec avformat cdda dbus dts dvbpsi dvd egl encode ffmpeg flac gcrypt kde libnotify mmx mp3 mpeg ncurses ogg opengl png postproc qt4 sdl sse svg swscale truetype udev vorbis x264 xcb xml xv -aalib (-altivec) -atmo (-audioqueue) -avahi -bidi -bluray -cddb -chromaprint -dc1394 -debug -dirac -directfb (-directx) -dvb (-dxva2) -faad -fdk -fluidsynth -fontconfig -gme -gnome (-gnutls) -growl -httpd -ieee1394 (-ios-vout) -jack -kate -libass -libcaca -libsamplerate -libtar -libtiger -linsys -lirc -live -lua (-macosx) (-macosx-audio) (-macosx-dialog-provider) (-macosx-eyetv) (-macosx-qtkit) (-macosx-quartztext) (-macosx-vout) -matroska (-media-library) -modplug -mtp -musepack (-neon) -omxil -opencv -optimisememory (-opus) -projectm -pulseaudio (-qt5) -rdp -rtsp -run-as-root -samba -schroedinger -sdl-image -sftp -shout -sid -skins -speex -taglib {-test} -theora -tremor -twolame -upnp -v4l -vaapi -vcdx (-vdpau) -vlm -wma-fixed -zvbi" 19,151 kB
[ebuild     U ~]      media-libs/phonon-4.7.2 [4.6.0-r1] USE="qt4%* vlc* (-aqua) -debug -designer% -gstreamer* -pulseaudio (-qt5) (-zeitgeist)" 323 kB
[nomerge       ] media-video/vlc-2.1.2:0/5-7  USE="X a52 alsa avcodec avformat cdda dbus dts dvbpsi dvd egl encode ffmpeg flac gcrypt kde libnotify mmx mp3 mpeg ncurses ogg opengl png postproc qt4 sdl sse svg swscale truetype udev vorbis x264 xcb xml xv -aalib (-altivec) -atmo (-audioqueue) -avahi -bidi -bluray -cddb -chromaprint -dc1394 -debug -dirac -directfb (-directx) -dvb (-dxva2) -faad -fdk -fluidsynth -fontconfig -gme -gnome (-gnutls) -growl -httpd -ieee1394 (-ios-vout) -jack -kate -libass -libcaca -libsamplerate -libtar -libtiger -linsys -lirc -live -lua (-macosx) (-macosx-audio) (-macosx-dialog-provider) (-macosx-eyetv) (-macosx-qtkit) (-macosx-quartztext) (-macosx-vout) -matroska (-media-library) -modplug -mtp -musepack (-neon) -omxil -opencv -optimisememory (-opus) -projectm -pulseaudio (-qt5) -rdp -rtsp -run-as-root -samba -schroedinger -sdl-image -sftp -shout -sid -skins -speex -taglib {-test} -theora -tremor -twolame -upnp -v4l -vaapi -vcdx (-vdpau) -vlm -wma-fixed -zvbi"
[ebuild  N     ]  net-dns/libidn-1.28  USE="nls -doc -emacs -java -mono -static-libs" 3,395 kB
[ebuild  N     ]  media-libs/libdvbpsi-0.2.2  USE="-doc -static-libs" 323 kB

Total: 5 packages (1 upgrade, 4 new), Size of downloads: 23,248 kB

The following keyword changes are necessary to proceed:
 (see "package.accept_keywords" in the portage(5) man page for more details)
# required by media-libs/phonon-vlc-0.7.2
=media-libs/phonon-4.7.2 ~amd64
# required by media-libs/phonon-4.7.2[vlc]
# required by kde-base/phonon-kde-4.13.3
# required by kde-base/kdebase-startkde-4.11.11
# required by @my-kde
# required by @selected
# required by @world (argument)
=media-libs/phonon-vlc-0.7.2 ~amd64

Use --autounmask-write to write changes to config files (honoring
CONFIG_PROTECT). Carefully examine the list of proposed changes,
paying special attention to mask or keyword changes that may expose
experimental or unstable packages.