Samsung has started pushing the Android 5.0.2 OTA update to both the Wi-Fi only and the LTE-enabled versions of the Samsung Galaxy Tab 4 10.1, although the rollouts for the two versions initiated in different corners of the world.
Your tablet will notify you when the update is available for download, as the device will regularly check for the availability of new software updates. To manually check for the new update, you can head over to Settings -> General -> System Updates -> Update Now.
The 5.0.2 Lollipop update will bring a number of improvements to your Galaxy Tab 4 10.1, such as a new TouchWiz UI with Material Design elements, a new notifications panel, a new multitasking menu, as well as a new lockscreen with improved notifications. Under the hood, the Lollipop update also comes with the usual range of performance improvements and bug fixes.
Now that the largest tablet in the Galaxy Tab 4 series is being updated to 5.0.2 Lollipop, the 7-inch and 8-inch flavours will probably start receiving the Android update in the near future as well.