SCOTUS does have the option of holding cases over from one term to the next. Particularly with Duncan v Bonta (the California Mag ban and confiscation challenge) denying that would put the citizens of California in a very rough spot. Keep their >10 round mags and become a felon if discovered, or find some means of complying and not keeping any >10 round magazines in state.
This would be a travesty beyond anything contemplated to date and regardless of what other "more important" things they may believe are on their plate, would be reprehensible because they were "too busy".