PySide2 (Qt for Python) has been in production where I work (and in the visual effects industry) since 2016.
Since then, bugs have been smashed, modules have been added and improvements have been made. I would recommend almost anyone to start developing with this right away and, like always, report bugs [0] and contribute improvements back to the project [1] (not on github).
Would it be as simple as a global change of all "from PyQt5" to "from PySide" in all import statements?
Almost, when switching from PyQt4 to PySide 1. It was roughly equivalent with some minor differences. It was much less work than switching Python 2.7 syntax to 3. There are some bindings as well [1].
I don't know much detail about PyQt5 vs PySide 2 but at least the overall logic should be the same.
[1]: https://github.com/epage/PythonUtils/blob/master/util/qt_com...
PyQt5 and Qt for Python is a 1-to-1 binding to the original Qt and their APIs are almost identical, so you should be able to switch to Qt for Python quite easily when it is stable.
By the way, Qt for Python is re-branded from PySide2. They are the same.