I think after 30 days it will close, but is it wise to do nothing? The buyer could escalate at any time now, and get a refund, but you would get a defect.
Defects can be serious for a seller as ebay expect no more than a 2% defect rate, above that and a seller falls to below standard. If the purchase was very low value, it would be very much in your interest to get the case closed, as even if case runs out of time, buyer still has 60 days in which to leave feedback.