The thought that people would unitedly leave Reddit was delusional.
I expected that only a small portion of people would really leave. I think there will be another small wave of leaving people when the 3rd party apps stop working.
But reality is: most humans don't like change, most humans like convenience. Forums like this are made by a minority, who share knowledge and time and take time to help others out. The vast rest of members is lurking and meme posting.
But I expect the majority to stay, at least now. Probably this blackout helped developing new forums though and maybe Reddit's popularity will slowly fade, we will see.