The first is many companies will return to requiring a majority of time in the office. There are admittedly hard to measure reasons management will want back in the office, and the first is productivity (I don’t mean how much an IC produces, but how much revenue per employee a firm generates).
The second future is all our tech jobs get offshored, similar to what happened after the dotcom bubble burst.
I believe that companies will probably wind up going to future #1. Or at least companies that are heavily invested in R&D.
There will probably be more satellite offices and more geographically distributed tech startups.
But in the first future I believe SF and Silicon Valley will still serve as one of the largest tech employment hubs. For example NYC is still a major financial hub, despite major top-25 US banks being headquartered in places like Texas, Virginia and North Carolina.
Edited to comply with Dang’s reminder of site guidelines.