Re: This happens all the time
"I know people who've been working for Google and other SF employers who're desperate to move away from $4500 rents, especially when they're looking at starting families."
We'd need the Second Dotcom Bubble to pop before it will make any difference. Companies are 100% bought into the idea that "disruption-enabling" tech talent only lives in Seattle, SF/SV and maybe NYC or Boston. Otherwise, why would they be paying $200K+ for SREs and developers even if they are swimming in more money than they can ever possibly spend? The tech companies are desperately trying to hang on to their top people, and whether or not it's true there is this perception that top tech talent is only interested in lavish upscale city living.
Even where I am in suburban NYC, around me the IT scene is quite boring...healthcare, education, a couple IT service providers and a handful of old-school companies that actually make physical products if you can believe it. If I wanted a Dotcom Bubble job I'd have to get on the train and go to the city...something I've managed to avoid since...surprise...I have a family that I'd like to see once in a while and a 3 hour daily commute isn't compatible with that.
What I think will happen is what you're describing...this latest crop of new grads will get tired of working crazy hours, might develop a life outside of the office and want to start families. I'm involved with a lot of AWS and Azure projects and I can tell Microsoft and Amazon are running their engineers ragged pumping out service after service every 2 weeks. Even the smartest, most work-focused people out there have a limit.