I think it depends on how many other states jump on the bandwagon. If it is just CA, even all sales to that state, as large as the population is, are a tiny fraction of gun sales to the rest of the states. I think the mfgs will balk, and tell CA politely to "go to hell".
The problem for the gunmakers is they’d have to develop “boutique guns,” specially made by state. That would *really* drive the prices up, so some sort of standardization would have to be developed, all to the detriment of the right to keep and bear arms. All the while, the science is dubious. You don’t even need to be a gunsmith to defeat the microstamp. Just run a couple thousand rounds of good ammo through the gun and the mark is illegible. Or go at the firing pin for a couple minutes with some emery. Online sales of replacement firing pins will become a cottage industry.
It’s like gasoline: California demands certain blends of fuel, and the people living in the nearby states all have to burn it (and pay extra), even though they had nothing to do with mandating it. Taxation without Representation.
Meanwhile, two major gunmakers just told CA to, as you put it, “Go to Hell.” Good for them.