He did, but that was 2 years ago. Time has moved on, and GF1 (indeed all of Northern Nevada) is severely labor constrained for the forseeable future.
No resources to waste in Reno. Chronic labor shortage has reduced Panasonic's nameplate 35 GWh/yr capacity to just 24 due to them not being able to hire and retain staff.
2 days ago 'carsonight' wrote that Panasonic hired 75 people at a job fair in Reno, but only 40 of them showed up for work on the 1st day. At GF1, they can't even man the equipment they've already paid for and installed.
I agree a new Sprung structure likely is coming to the west parking lot at Tesla Fremont. That way, they can use the spare capacity of the existing Schuler presses for body stamping, and extend the existing paint shop rather than having to start from scratch. Seats are also made just 2 miles away, as are many other components shared with Model 3, then there's easy access to the new Lathrop Distribution center.
But I think Elon's long term vision for manufacturing centers around robotic vision. FSD Computer hdw and infrastructure is a first step in a long march toward that goal. Its what he needs to build a city on Mars, and he wants to be ready to start that in about 10 years. Tesla's literally his makerspace.
Cheers!