What scared away all but one of the potential bidders in RealD? That’s still unclear, although a new SEC filing from the 3D technology company cites others’ concerns about “perceived risks around consumer appetite for 3D films,” as well as fears that theaters might not renew their deals to license RealD technology. Early this month RealD wrapped up a hunt for a buyer, which began in February, by accepting Rizvi Traverse Management’s offer of $551 million, including…