20 May 2019
Samsung started upgrading Galaxy Tab S4 to Android 9 Pie last month. It was an update released for select markets including India, Brazil, and France. It seems like it was some kind of testing rollout where the team wanted to test the software for undiscovered bugs and issues ahead of the public release. The test appears to have been completed as a wider rollout of the update has now begun.
The Samsung Galaxy Tab S4 Android Pie upgrade is now rolling out in countries like Bulgaria, Germany, Greece, Hungary, Italy, Israel, Kazakhstan, the Netherlands, Poland, Portugal, Romania, Singapore, Slovakia, Switzerland, Ukraine, and Uzbekistan. Since there are countries from all different parts of the world, it is safe to assume that Samsung has kicked off global rollout for the latest Android version.
It is an over the air update which means it will be arriving on your Galaxy Tab S4 unit anytime soon. Just keep internet connection enabled on the tablet and you should be receiving an update notification. If you want to check for it manually, you can do that as well,
One thing to keep in mind is that the current rollout of Android update is only for the LTE variant of the tablet. If you have a non-LTE variant, you will have to wait for some more time.