I mean the same thing is happening at Twitter, but most users are staying there because there's nowhere to go. Bluesky is invite only and mastodon doesn't have whatever celebs and influencers they follow (and no shade on these folks, I originally joined Twitter for a single person's tweets).
This place is cool, but people will stay on Reddit as long as their communities do. And frankly I think most people are going to go to discord if Reddit does actually die, because most subreddits already have an associated discord channel