Inertia is a thing, both in a positive and negative way. What I mean by that is, you can reach a threshold where people are leaving fast enough that Reddit will lose more people than not (positive from our current point of view).

The other way it works is people are just so used to Reddit and the habit returns quickly once the blackout is over (negative from our point of view).

Which way will this go? My pessimistic outlook is that tons of people are exploring Lemmy/KBin/whatever fediverse thing now while they have a Reddit sized hole in their daily routines, but once Reddit is back they will go back there. I think this is shown in how Twitter users bailed off pretty hard at first and Mastodon got a bunch of new people but those people slowly went back to Twitter. Some people will stay at the new place for sure, but a lot won’t. None of that is really a problem per se, either.