At most, I could see specific cases that have been excessively dragged out being struck down by the courts while leaving open the possibility that once the kinks in its system are straightened out, California would be able to resume implementation of the death penalty.
If that happens, I suspect than some representatives and senators may decide to do like Canada did for abortion. Having the court saying to rewrite the law, but failing to pass another law about it.
Would be de facto abolition, without the negative consequences on them.