You left one thing out.
They will need to raise a formidable army, navy, and air force and quick because the Federal government is not going to lose 3/4s of the nation’s western coast without a real, no kidding gunfight.
Giving them a whiff of grape will probably be enough.
Maybe this time we will have the good sense to actually hang the secessionist leadership after defeating them.
The only thing less certain or possible than California seceding is the chances of CA being invaded by the US Army.