This seems to be the successor for PySide that supports Qt 5. The old PySide died some years ago and only PyQt was offering Qt 5 support. Due to some details PyQt was never officially supported by Qt. Is PySide2 now officially supported by Qt?
"PySide2 – the bindings from Python to Qt – changes skin this spring. We have re-branded it as Qt for Python on a solution level, as we wanted the name to reflect the use of Qt in Python applications. Under the hood it is still PySide2 – just better."
The owners of PyQt (Riverbank) depend on that product to survive; whereas Qt has bigger fish to fry most of the time. The incentives are very different.
Digia later spun off The Qt Company, which develops Qt and is now developing PySide2, so this is actually the first time the same organisation has developed both Qt and Python bindings for it.
For many purposes (including mine), PyQt is very expensive, so I'm really hoping PySide2 goes somewhere.