Seems a bit megalomaniacal.
"I'm not interested in doing this any more. Therefore I'll shut it down for everyone"
This way, people have been given plenty of advanced notice and can start their own forums somewhere instead. I'm sure each of the 300 subforums already has some people running them, and they could do the above if they actually cared.
I find it hard to believe someone will take over 300 forums out of the goodness of their hearts and not start making it worse eventually, if not immediately.