This might be a problem for one or two of the top areas, but there are not enough Bay Area emigres to materially move the needle in the vast majority of non-Bay Area localities.
Try "tens to twenties of 'top areas'". Just look at the housing market in any other city in the US that's started to build a tech hub. Austin, TX in particular is a good example where the average cost of a decent house has basically doubled in the last 10 years.
This is what has happened in Austin and Portland, just to name two. As another commenter said it isn’t enough to affect every market but I think it affects many markets, and there is a domino effect as people cash out of those second level cities and move into third level, etc.
"Relatively affordable" to people coming from the Bay Area translates to "completely out of the question" for people who are from the areas affected.