On Google+ today, Motorola's David Schuster announced that the AT&T version of the 2nd generation Moto E would be receiving its Android 5.1 soak test today, meaning a general OTA shouldn't be far away.
Global versions of the Moto E 2nd Gen have generally already received this update, so if you want a changelog, it's right here. Android 5.1 brings new notification and interrupt settings, an enhanced quick settings panel, Android's Device Protection feature (with factory reset protection), and more. Of course, this will also bring a litany of bug fixes (and probably new bugs!) specific to Moto E owners. Again, this soak is specific to the AT&T GoPhone LTE model.