Aggregate price for talent probably doesn't change. Demand for talent in key markets goes down (as companies in those markets start looking for non-local talent[1]), but demand for talent in
any market goes up (as non-local companies seek local talent).
So it would follow that overpriced talent in high-demand markets would see a decrease, where underpriced talent in low-demand markets would see an increase.
This would be the same concerns with offshoring as well, but that hasn't led to massive salary drops. Because there's still a big cost to switching people. If you could fire all your SF SWEs today and replace them with identical, knowledgable, fully-ramped, culture-carried SWEs in $secondary_market for half price, you would. You can't, so you threaten and you try to convince your SF SWE that you could just enough to keep their expectations low, but not so much that they actually quit.
I see a lot of companies still trying the "CoLA trick" on employees moving to secondary markets. "We can hire your position in $market for cheaper," so the argument goes. The best move there is to call their bluff: "go do it then". Most people won't do it because a) conflict is hard and b) finding a new job on top of moving is annoying. So they'll take it on the chin and just resign 6-12 months later after they're settled.
[1] In the old world, there's still a premium to convince talent to relocate. So companies in high-demand markets (e.g., SF) either have to pay +x% to tap non-local talent and get them to move to the high-demand market (where they become local talent).
Even in the new world, non-local talent isn't going to sit by and let themselves be underpaid. "I'm doing the exact same thing, delivering the exact same value, but someone is getting paid 30% more to sit in the office? Oh, and you don't even pay for my home office?"