I upgraded yesterday, losing Samba (meh) to the Python changes.
Checking on full-upgrade today, there were lots of things on threat of removal (mostly mail related):
The following packages will be REMOVED:
akonadiconsole akregator digikam digikam-private-libs kalarm kde-standard
kdepim kdepim-addons kdepim-themeeditors kmail korganizer
libkf5eventviews5abi1 libkf5incidenceeditor5abi1 libkf5mailcommon5abi2
libkf5messagecomposer5abi1 libkf5messagecore5abi1 libkf5messagelist5abi1
libkf5messageviewer5abi1 libkf5mimetreeparser5abi1 libkf5templateparser5
libkf5webengineviewer5abi1 libkpimimportwizard5 libkpimitinerary5
mbox-importer pim-data-exporter pim-sieve-editor
Probably another small transition period, but keep your eye out and check on any warnings before you press "y".