Update 6

Update 6 is an upcoming major game update for, and is due to be released in early February. It will be the largest update ever to be released for the game, and the update is the size of two normal updates in one.

The sixth major update will contain a complete overhaul of the Veteran System known as the Champion System, the all-new Justice System which allows players to commit in-game crime, a revamp of Provisioning and many changes to combat, among tons of other improvements.

Features
NOTE: This list is likely incomplete, and will be immediately updated once the full patch notes of the update become available shortly after the beginning of January.
 * Champion System Part 1 - Advance your Veteran-level characters a different way with this new type of character progression. Become more powerful by advancing in 9 Constellation trees and gaining better stats as a result. Part 2, due in Update 7, will remove Veteran levels entirely. The Champion System is due to add 3 real-world years' worth of progression.
 * Justice System - Become a criminal or a guard in an all-new type of gameplay. As a criminal, you can murder, steal from, pickpocket, break into the homes of, and assault every NPC in the game - but don't get caught by guards or you'll obtain a high bounty and a heat meter, as well as a greater infamy level. As a guard, you are able to halt the doings of such troublemakers. More info on the system here. (Page to be added soon).
 * Provisioning Overhaul - The crafting skill Provisioning has gone through a complete revamp, and Fishing will now be integrated with Provisioning, and many quality of life tweaks and changes to recipes have been implemented. Info here.
 * Combat Revamp - New animations for combat have been implemented into the game, and many changes to skills, stats and armor have been introduced. Heavy and Medium armor have been improved and every player stat has been increased by 10 times for all levels. More abilities and spells such as Magicka Bomb are on the way, too.
 * Balance Pass - Many changes are on the way for each of the four classes in order to obtain class balance in PvP. One of such tweaks is to the Dragonknight ability Reflective Scales, which will now only reflect 4 spells at a time instead of an infinite number.
 * Tweaks to Inventory Management - A new UI is being added for vanity items such as pets, trophies and costumes so that they no longer take up valuable inventory space. You can also switch your mount on the fly in this new menu.
 * Expanded Delves - All delves in Greenshade, Rivenspire and Shadowfen have been enlarged, and contain more monsters and loot. Additionally, some delves in Auridon, Glenumbra and Stonefalls will be enlarged, the names of which are unknown. This is part of an ongoing process to make all delves in the game larger.
 * Hundreds of bug fixes, quality of life tweaks and overall improvements and polish.

Trivia

 * Update 6 is currently the largest known update to the game.
 * The Champion System alone will add about 25,200 hours' worth of character progression, or about 3 real-world years. This will make ESO the largest game in the entire series in terms of content.
 * Update 6 was officially unveiled on December 4th.