Personally, I was on a couple support groups, and only like one has moved here, so far. I think, like always, people will find another space to setup shop. Hopefully it'll be here, but it'll be somewhere, if they don't stay on reddit.
As for the ones on reddit, I think they will keep chugging along, but I think the content/help/info will take a pretty big nose dive. Between moderators leaving, and the influx (it was already a real issue) of bots, and the lack of the bigger users/contributors, I don't think they will be nearly as helpful/informative as they were.