The Galaxy Tab Pro 8.4 was released in 2014 and was never updated.
The Galaxy Tab S 8.4 was released in 2014 and got one update, to Android 5.0.2.
The Galaxy Tab S2 8.0 was released in 2015 and is getting one update to Android 6.0.1. Chances are it won't get another one.
So they may support...