The California Supreme Court has said it will hear oral argument in Patterson v Padilla, S257302, no later than the week of November 4-8, 2019. Conceivably it could be earlier. This is the case over whether the California Constitution permits the state to enforce its law that presidential primary candidates must reveal their tax returns. Patterson, the first-named plaintiff, is the state chair of the California Republican Party.
Although a U.S. District Court has enjoined that law on federal constitutional grounds, the state is appealing that to the Ninth Circuit. Therefore it is still sensible that the State Supreme Court will hear the state constitutional case. The state constitution says that all “recognized” presidential candidates (who are seeking the nomination of a qualified party) must appear on a presidential primary ballot.