Hello,
the person in charge of KDE in debian made some uploads to sid of packages which belong to Plasma 5. This is breaking KDE SC 4 while at the same time plasma 5 isn't available in debian sid.
I also have reasons to think that his intention is making plasma 5 available soon, however I'm not completely sure because since Ieft the debian qt/kde "team" this kind of things are being done unnanounced.
Since the person in charge of KDE in debian seems to insist in breaking KDE SC 4 and it's not very feasible to fix all the continuous incoming breakages and Plasma 5 will be uploaded to sid sooner or later:
in a few hours or days the plasma 5 packages available in the kdenext/kde-frameworks repository will be moved to kdenext/unstable.
Fortunately our Plasma 5 packages are reasonably mature although not perfect. Note that they are available here in siduction for more than a year, thing which allowed us to improve the packaging and be ready for this little apocalypse.
What to do to "survive" gracefully:Option a: Do NOT dist-upgrade and stay with KDE SC 4 for a while; if you already upgraded some packages that you shouldn't the breakages can be undone, you can ask for help here. This option is only reasonable as a temporary solution while you find some free time to go for the option b or c, see below.
Option b: Install Plasma 5 in other hard disk/partition; grab a siduction indiansummer iso, install it and upgrade to Plasma 5 following the instructions here:
https://community.kde.org/Plasma/InstallingNext#siductionOption c: Make backup and upgrade your existing Plasma 4 installation to Plasma 5. Instructions here:
https://community.kde.org/Plasma/InstallingNext#siduction Keep in mind that you may need to reconfigure some programs or things in Plasma.
I would recommend you the Option b. It's the option I did for myself and I'm now writing this message from my new Plasma 5 installation.
Cheers.
EDIT #1 (Friday, 3 July 23:12 zulu)The KDE Packages were copied from kdenext/kde-frameworks to kdenext/unstable as announced above; this way Plasma 5 becomes the default for siduction.