Does the state government still want to buy the castle?
I am not sure - don't live in that part of Germany. There was a public debate about it whether it was worth spending so much money on another castle ... and now with Corona. But I have no idea.
In March 2019 EA Junior established a trust "Castle Marienburg", because he could not sell it to the county of Niedersachsen because of the pending lawsuit of EA Senior.
I guess that his lawyers recommended it to him.
In the meantime the castle is still being used for exhibitions, as a museum and for events (as soon as Covid-related restrictions are over). The renovation and maintenance costs are hugh (similar to many old castles in GB) so the family had to think about alternative options .
EA senior probably has lost all sense of reality because of his health issues. The family can be happy that EA Junior is such a sober and smart eldest son.
EA Senior does not accept the ban that was put on him, not being permitted to live at his house in Austria for three years. That's where he attacked the police and his housekeepers. I am sure he will sue again, because where will or can he live? Strange, owning several castles but no place to live?