Leaving the OSC is a common practice done by Memebers, usually to get attention and support, ususally in the midst of Drama. Most claims of leaving are done through "I'm Leaving" Journals, in which they site multiple reasons for why they are leaving, most of said reasons being almost universal traits of all communities, or minor complaints that often barely affect the community in the first place, such as the lack of Object Shows.
And for all the people who are saying the community is dying, you're all fucking idiots, the amount of fanfics a community has and the rate at which the main show comes out is not the sole deciding factor of the size of a community, if that were the case fandoms for shows like Invader Zim and other old cartoons would be dead.
Most people who make these journals come back in like a day, usually claiming they aren't in it, but still post almost entirely object-related stuff in spite of that. Either that or they claim to be out of the OSC, but still talk to people in it, which according to the definition of Community, makes them part of the OSC.