I'll stick around as usual until something more disastrous shows up. Then when it does, I'll have fun playing with it like a dead raccoon. I tend to prefer lightly moderated or completely un-moderated communities anyway, even when trolls do happen. It makes things more colorful, vibrant and unpredictable. Sort of like playing hot potato with a live hand grenade.
I've known a few people who've tried getting old abandoned forums deleted, and apart from a very grave TOS violation such as child p0rnography or a major piracy trade, it generally doesn't happen due to respect for the original Administrator's account. Otherwise, much of the time it takes nothing too short of a valid legal threat/order from a court, law enforcement agency or attorney.
Create-a-Forum, ForuMotion, ProBoards, etc. could technically shut down a forum for even very minor TOS violations like silly spam or even minor swearing, but doing so would cause bad publicity, cost them traffic and advertising, and pose a risk of gaining a reputation as an unstable forum provider.