"In the long run, we're all dead." -Keynes
It took generations for a second Motor City to emerge outside of Detroit. New York is still the unchallenged capital of the finance and fashion worlds. There's no "Second Hollywood" in the United States. There's a Reno and an Atlantic City, but neither holds a candle to Las Vegas.
What makes you so certain tech will have an exodus from San Francisco between now and the year of your retirement?
Look into what's been going on in Georgia for the past few years. Not a replacement for Hollywood yet, but it's a good example of how quickly alternatives can take off due almost entirely to geographic differences in the cost of doing business.
The costs of doing business in Atlanta are significantly less than other regions.
And while they likely have convinced a few companies (they like to showcase a half dozen or so), it's not like it even was a measurable blip on the growth of game companies in Silicon Valley.
Most people don't realize it, but many recent high-budget movies were filmed in Georgia, e.g. Fast Five, Vacation, Ant-Man, all three Hunger Games movies, one of the recent X-Men movies, Flight, etc. After 2008, there was an abundance of empty warehouse space here available at deep discounts, not far from the highest volume airport in the world.
As the economy rebounded, momentum in that industry seems to have remained even though there aren't many empty/cheap warehouses here anymore. A few developers are even working on purpose-built movie studios around town now.
It has been interesting to watch, and certainly could parallel what could happen in the bay area if an exodus to somewhere like Austin began in earnest.
Tech Austinite here -- given the rate prices of food, housing, etc. are spiking here, I'm presently more inclined to see ATX as catching up to SF prices and acting as an SXSF than remaining a low-cost alternative.
Don't generally disagree with your thesis, but at least for tech I don't think the game is zero sum, and the market is expanding fast enough to support multiple tech hubs.
It's right here in Atlanta. It's been a decade and a half in the making, and the pace and scale of it increases with every passing year.
Pinewood: http://m.pinewoodgroup.com/our-studios/usa/pinewood-atlanta-...
Third Rail: http://clatl.com/freshloaf/archives/2015/04/07/film-and-tv-s...
Tyler Perry's new facility: http://m.clatl.com/freshloaf/archives/2015/06/29/tyler-perry...
This is just three of about ten studio facilities being built in the area.
I believe three of the Marvel films have been filmed in Atlanta. These have been recent enough not to be in that list.
I know this is anecdotal, but if you were living in Atlanta you'd get a sense of how much growth is occurring in our film industry.