I am theoretically switching over from Reddit to Lemmy. Finding myself spending more time on Lemmy than on Reddit. Maybe it’s because I am limited to using the desktop and can’t aimlessly browse Reddit on my iPhone. Of late, the only subreddits I cared for were on sports and their matchday threads and r/watches. I found myself aimlessly browsing through r/AskReddit and asking and answering pointless questions.
You can use Lemmy Explorer to search all the (900 or so) Instances for your community. If those Instances are federated with this one (most of the are), you can subscribe and post into that Instance’s community without having to create another account.
When Reddit collapses for good, it will be the end of Lemmy. There will be nothing to talk about, no subject to talk about.
I think it depends on what people make of it. Forums existed well before Reddit and Lemmy can scratch that itch. But so far a lot of the discussion has focused on Reddit and if real content doesn’t replace it then Lemmy probably will fade away.
Also, devs can make a difference. If the experience gets better both on web amd mobile then it will help.