Sometimes updates don't happen entirely on schedule, the next you get will no doubt be UI 4 because the same happened with my Tab A7 after only getting a Google Play Services Update the previous time it was due a quarterly firmware bump. The reason is not that it's a lower tier device at all though, the same happens all the way through the Samsung range occasionally and indeed with other manufacturers. There's a few caveats when reading such published schedules, first they will pull a patch or not release it at all if it's unstable, second the patch has to be approved for use on mobile networks by regulatory bodies in some countries including the UK and finally the phone network provider also needs to sign off on it. Tablets without LTE shouldn't be delayed as much but they are. The LTE models get dealt with before the wireless only models are patched normally.
