I think a lot of the survey is accurate. There will be a lot of people that decide to permanently relocate. It's already visible in the market data from rent because even as people are considering leaving, the second side of the equation is that people have stopped moving in.
These two factors together will create a shift whereby for the next two years rents will drop, however after that, as the world moves forward and recovers, SF will ultimately rebound as other metro areas as well.
This will be a short term solution, to a long term problem, in that there isn't enough housing supply in SF for the next decade unless this trend is permanent, which I don't believe that it is.