According the MacRumors, yes but they cant confirm if its only for the new AirTags yet:
"watchOS 26.2.1 is also coming, and it expands Precision Finding to the Apple Watch Series 9 and later, and Apple Watch Ultra 2 and later. We have not yet confirmed if this is for the new AirTag only or also works with the original model."
"watchOS 26.2.1 is also coming, and it expands Precision Finding to the Apple Watch Series 9 and later, and Apple Watch Ultra 2 and later. We have not yet confirmed if this is for the new AirTag only or also works with the original model."