yes, the pythonscripting next is only available for openHAB >= 5.0.x and < 5.1.x
for openHAB >= 5.1.x, I will create a new marketplace version as soon as it is needed.
The idea of “pythonscripting next” is, that it contains all changes which are not merged yet, but stable enough for daily usage.
There is also a version for openHAB 4.3.x, based on the same codebase. But this is beta, because some changes in openHAB Core are missing, which are only available in openHAB >= 5.x.x