When we compare the the Gear S3 and the Gear S2, the differences between the two are quite substantial in both hardware and to some level software to prove that the Gear S3 is the better device. But shift that comparison to a generation ahead with the Gear S3 and the recently launched Gear Sport smartwatches, the differences in proving that the Gear Sport is the better device is mostly on the software level than in terms of hardware (with a couple of exceptions ofcourse).
This is because, the Gear Sport was more of a new category of smartwatches rather than a direct successor to the Gear S3 as that void will soon be filled with the announcement of the Gear S4. But, the Gear Sport being a new smartwatch does have one major standout point when compared to the Gear S3. The Gear Sport happens to be the only wearable currently to run on the latest Tizen 3.0 OS meanwhile the Gear S3 is still on Tizen 2.4.2 and thus misses out on a number of changes and improvements when compared with the Sport.
However, according to the folks over at Android Pit, the Gear S3 will not be abandoned by the Tizen 3.0 as Samsung will soon be pushing an update to the Gear S3 to bring the software on par with the Gear Sport with Tizen 3.0. While the software update can't bring features like swim tracking to the Gear S3 as it lacks the 5ATM water resistance found on the Gear Sport, the software update will likely bring improvements in over all functionality.
Some major improvements that we could expect with the update are better syncing over Bluetooth and WiFi with the smartphone, smoother UI and a new system wide theme that we have seen on the Gear Sport, better battery life, real-time heart rate monitoring, accurate activity tracking. The last set of features that could come with Tizen 3.0 is the ability to control Samsung IoT-enabled devices through Samsung Connect and being used as a controller for the Gear VR.
While we are just making plain assumptions here, there's a high probability of these features to actually make their way on the Gear S3 with Tizen 3.0.