He may leave a factory there for costs, but he most certainly is expanding and migrating to Texas. Hell, I bet he's about to shill the hell out of his battery storage tech there too.
how well does grid battery storage do in that kind of weather?
IIRC, mobile battery solutions have about 20-30% losses in freezing temps.
Fixed utility scale installations can regulate temps using geothermal and solar energy to reduce losses due to extreme weather.
Not just the factory, there is both Tesla and Space X HQ in CA. And if you look at careers page for both, overwhelming number of job openings are there. In addition, Tesla has expanded like mad in Fremont and further East Bay. Including owning several warehouses and offices in the region