Judging by what I’ve seen of leftists on reddit, I predict it will most than likely go okay for a while, slowly getting more and more toxic and exclusionary as time goes on, before imploding due to in-fighting.
I’m 50/50 on if I’m being optimistic by putting it in such a way that it will be a slow descent, and not a freefall from the moment it starts. Further 50/50 on if it’s implosion is caused by some reddit-style media attention over something shitty they do - while not a statement on the left in general, reddit leftists in particular seem to still have a lot of problems with racism, sexism, anti-semitism, transphobia, and other forms of bigotry. They’re not as bad as reddit on the whole, but that’s a bar to pass that’s so low, you need specialized geologists to locate it.