The new software version was released with assembly numbers R600XXU2FUD1 and R760XXU2FUD1, respectively. The Samsung Gear S3 has been updated with improved Wi-Fi performance and bug fixes. Regarding the changelog for the Gear Sport, it is unfortunately not there. Most likely, the developers added the same improvements to the software.
According to our colleagues from SamMobile, the system has been released for smartwatches in China so far. In other regions, the update will appear a little later.