It really depends on how the city chooses to restrict housing supply; we have the technology to ensure that housing is affordable, but most American cities make deploying said technology illegal: https://www.amazon.com/Rent-Too-Damn-High-Matters-ebook/dp/B....
This is a fact of policy, not nature: https://www.bloomberg.com/view/articles/2018-03-14/californi...
There is an undeniable correlation between more people with more money to spend and increased cost. Go look at tourism economies for an example.
But even leaving that aside, guess what's not going to be at all reassuring to current residents of whatever city is gonna be the "next Silicon Valey" or even "next Austin"? "Oh, don't worry, rents gonna go up a LOT, but it's still gonna be affordable for MOST PEOPLE IN TECH. Just not most of y'all that lived here before all the techies got here."