It would take much longer and much more data to form a trend. Now is just all speculation. The first wave leaving would be people without strong ties to the B

It would take much longer and much more data to form a trend. Now is just all speculation. The first wave leaving would be people without strong ties to the Bay Area (layoff, no work, etc). They tend to leave for other regions, like you said. The second wave would be people still working in the region but cannot stand the deterioration in the big cities. They will move to the burbs.