That's what Tokyo is; increasing in population despite Japan as a whole falling. People in cities have smaller greenhouse gas emissions than people living rural or suburbs; they don't need cars because things are close and mass transit is affordable and convenient because there are enough people sharing it. The US can't get there until they enforce standards of conduct in the public sphere and stop exclusionary zoning.

>forcing SF or other popular hubs to build high rise

Just a note but I find it highly disingenuous to conflate eliminating restrictive zoning with mandating high-rises. Eliminating restrictive zoning is just allowing the free market to better utilize land, which may mean high rises, or it may mean tightly packed townhouses or single family homes like in many Japanese suburbs, and only where the demand exists. If you own a standard American SFH, nobody is forcing you to demolish it.

>just make them even more popular and further increase the gravitational pull that will send another wave of migrants from the 2nd tier cities and we just repeat the same cycle with higher buildings?

Absolutely, without a doubt. There's a limit (globally it seems to be around a population of 30 million in the metropolitan region), but there's no doubt that if market forces brought reasonable prices to the Bay area at the very least the gentrified and priced out would return, those who fled to the exurbs and drive in for 70+ minutes would return, and at the very least a bunch of techies in other cities who could never imagine paying 3600 on a single bedroom would give the Bay area a try.

Essentially, the region would likely boom much in the way that New York boomed in the industrial revolution, or more recently Shanghai and Beijing boomed. Whether you view this as positive is obviously debatable but I find it undeniably fair that we stop stacking the deck in favor of the rich and landed