Honestly it'll probably be closer to 99.999% of users will stick around Reddit. The largest Lemmy instance is smaller than the smallest subreddit I follow and I suspect that's probably the case for most people.
Here's what will happen... Reddit blackout starts, people come to Lemmy, 8 out of 10 are confused by the way things work and bail instantly. 2 out of 10 might stick around, try to sign up, but everyone hammers the top 3-4 instances and they have a bad first impression. A few days later everyone is back at Reddit and Lemmy is right back where it was a month ago.
I hope I'm wrong, but I doubt I will be.
Opposite for me. Didn't work in Chrome before, but now when I go back it holds my spot.