As someone who is in the Glee fandom (looks at my Darren icon) i'm shocked about Mark. I mourned for him ages ago because of what was found on his computer though. If you really want odds about who may go next, I suggest Lauren Potter who played Becky Jackson. She has Downs Syndrome. Jane Lynch would be good odds too.
I can't see Lea Michele going without publicising it on Twitter or Instagram first.