Samsung Galaxy S5 Active from AT&T is getting a small OTA that is not Lollipop. The update is actually 4.4.4 with not much to say except that we have some miscellaneous improvements, some security updates and bug fixes on the way.
In order to get the OTA you can go to the update menu and manually pull it or you can wait for a few days to have it make its way to you. The update is a mandatory action so if you try to postpone it for too long, it will force its way to your device anyway.
Source: Samsung Support