The KDE-FreeBSD team bumped Qt to 5.7.1 and KDE Frameworks to 5.31.0 in official ports last week, so we're fairly up-to-date in that department. On FreeBSD, we still fully support Qt4 next to Qt5, so some of the delay in getting this stuff in is due to some shuffling of install locations. In particular, we've added qt-chooser in this round of updates, so that qmake is qmake -- and no longer qmake-qt4 or some other suffixed binary. We use qt-chooser to switch out one or the other. Checking that this doesn't break anything else -- or at least making sure that everything still compiles -- is what took the most time this round of updates.
So we're edging closer to getting Plasma 5 Desktop; TCBerner intends to import it together with all the KDE Frameworks-based KDE Applications. That makes it a grand shuffling of ports -- and that again takes lots of time.
I'm about to embark on an examination of kcheckpass -- we still have two of them, even, one kdelibs4-based and one kf5-based -- because the Plasma maintainers would like to clean up the code, and have asked distro's to double-check what actually gets used on each platform. (And kcheckpass is tricksy, like the time in 2003 or so I locked out all the sysadmins at the university by updating the KDE packages, but forgot to setuid it ..)
Anyway, the usual applies: Plasma 5 and KDE Applications are fine to use on FreeBSD, from the area51 repository, and official ports just keep getting closer, bit-by-bit.