Some case manufacturers believe that a previously-rumored refresh of the iPod nano is imminent, and have prepared new cases, notes MacRumors. The cases, from Italian accessory maker Puro, look to fit an iPod roughly the size of a fourth or fifth-generation nano, though seemingly wider — a tremendous turnaround from the current nano, with extruded pill curves resembling the second-generation nano and long-gone iPod mini. Rumors have suggested that…