Will you be allowed to keep them, or required to turn them in?
Depends if Trump wins in Nov., if Hildabeast or the Dems proxy wins, we will be forced to turn them in as SCOTUS will have an anti-2nd majority, which if that us the situation, surrendering our hi-cap mags wont matter as we wont have any guns to use them in. As soon as SCOTUS has an ant-2nd majority, CA's legislature will try to be the first to ban all guns outright, and there wont be anything that can be done to stop them.
Move to MT!
If SCOTUS has an anti-gun majority, moving out of CA will only be a stop-gap measure, once the Dems have both houses of Congress and Hillary/Dem is POTUS, guns will be banned nationwide, like with ACA, it wont matter what the State's want, they will allow comply with the Feds eventually.