Don't assume Tesla needs a new factory to build Cybertruck. With the projected late-2021 product launch, its uncertain Tesla could even build a new USA factory in that timeline.
Instead, I look for spare capacity and another shift on the Fremont S/X line to do final assembly for Cybertruck. Yes, that means a 17" horiz. display for S/X by then, along with the Refreshed/Plaid Model S, and more 18650 cells from Panasonic/Japan (hint: they are the SAME Tesla chemistry that goes in 2170s).
Telsa does not want to let capacity sit idle, as it does now at Fremont. Cybertruck needs no stamping, no body, no paint. Just bring pre-bent/welded hulls to final assembly. Cybertruck maximizes Fremont S/X line output ASAP, which I believe makes this plan tempting to Tesla's Board.
So possibly 50K Cybertrucks/year from 1 shift? Maybe slightly more with improving efficiencies. But I don't think this'll be the final answer. Consumers will demand more 21st Century high-tech trucks, and Tesla will find a new way to build them.
After SpaceX puts Tesla Cybertrucks on the Moon and Mars in the late-2020s, demand will literally skyrocket. Every future
James T. Kirk now growing up in Riverside, Iowa will loose his mind if he can't have one. I'll look for a new mid-West factory to build that 2nd Gen pickup truck.
As for Semi, I lean toward Lathrop. Telsa plans a 'small production run' in 2020, likely meaning ~500ish semi-trucks for their logistics needs. So any tent'll do, right?
Once they have some real experience building and operating Semi, I think they'll spec out a new line. I do expect Cybertruck to be first to production, though, at Fremont.
Cheers!