r$ddit will still exist for at least another 80 years bc there's always the chance someone will be like: "what was the name of that place I had that conversation on once...? let's see if it's still there..."
I signed up for the digg relaunch with the hope it can kill Reddit off for good.
I wish lemmy could do it, and the fediverse will always be there for the people who are willing to put in the tiny extra effort. But I think it'll take something centralized and easy to understand for the average person who doesn't care about that stuff to really make a dent and start an exodus.