Samsung Galaxy Tab S4 owners are in for a nice surprise
Before you get your hopes too high, it's worth noting that Samsung has just started the Galaxy Tab S4 roll-out, so for the time being the update is available in select countries. Also, SamMobile reports that only the LTE-enabled version is getting the Android 10 update at the moment, although it's safe to assume that the Wi-Fi only model will be upgraded too.
Currently, the update is deployed in France, so if you're located in this country and own a Galaxy Tab S4 LTE, you should be looking for firmware version T835XXU4CTF5. As far as the changes go, Android 10 comes with One UI 2.1 and a brand new June 2020 security patch.
Aside from that, expect lots of other improvements and new features, including Digital Wellbeing, Music Share, Quick Share, enhanced Dark Mode, Improved Accessibility, and a lot more. Also, many of the stock apps that come pre-installed on the Galaxy Tab S4 have been updated with new features.