The latest posting I saw was last week suggesting it was shutting down in late 2019. But honestly, who knows? There has been a tremendous exodus lately and the platform hasn't really fixed or addressed user issues or problems, so there's that. I just remember living through the whole LJ mess when Russians bought that platform. I can't guarantee when or if tumblr is going to go down, but I have been looking for replacement venues, which is why I ended up back here after an extended hiatus. :)