I moderate one significant sub on reddit, and we didn't take it down. However, we've also been trying to figure out what our alternatives are. And there aren't any that are a perfect match. The closest I've found so far is Lemmy -- which largely replicates the old-reddit/hackernews experience, but it is federated (which confuses a lot of people).
I set up a few communities on lemmy.ca (the Canadian node on the federated network), but I've no idea if users will follow. Feels like the digg exodus 2.0, except when everyone fled digg, reddit was already a viable option and the consensus pick. This hasn't happened this time.