CA never had a lane splitting law. Motorcyclists just started doing it decades ago because it made sense. It became accepted practice. Law enforcement also did it. So motorists in urban areas especially were just accustomed to it.
The few people who groused about it were informed there was no law specifically against it, so it was tolerated. For as long as I can remember the guideline has been no more than a 10 mph speed differential, and no blatantly reckless driving.
What CA is trying to do now, with the real push from LE on motors, is to educate and define. As scout said the vast majority of motorists are perfectly acclimated to lane sharing. Once in a great while some asshat (probably from out of state) will try to squeeze me out. Way more often people move over. No problem.
Motorcyclists are not going to be assassinated right and left, unless the culture in other states is incomprehensibly backward and angry. But the motoring public in areas not used to this will have to be educated because they aren't used to seeing m/c's coming alongside them. Drivers will be scared. Scared people get angry. Angry people do stupid stuff. That's the problem.