At least the ebuild indicates this. Qt4 is going away.
There is a newer upstream release 9.2.6 available with no indication of it being ported to Qt5, but if the use of Qt libs is basic enough it may be possible to build against Qt5.
Please try to bump and port from qt4-r2.eclass to qmake-utils.eclass and Qt5.
I was already working on 9.2.6 but got distracted by quite some things from real life...
But thanks for reminder. I am on it.
Done. New version in tree.
> media-radio/qsstv: Version bump. Switch to using QT5
> Fixes bug # 639256