During QuakeCon 2015, game director Matt Firor explained that the Elder Scrolls Online: Tamriel Unlimited would be receiving an expansion every quarter. The first is the already announced Imperial City expansion which releases on August 31, 2015 for PC and on PlayStation 4 and Xbox One on September 16 and 15 respectively. This expansion introduces the main city from Oblivion and will include,
…hours of compelling story content, expanded Veteran Ranks, a new currency for new epic gear, two new dungeons, never-before-seen monsters, craftable item sets, and more.
Next up is the Orcish city Orsinium during Q4 2015. Then the Dark Brotherhood and Thieves Guild will be introduced during the first two quarters of 2016. The factions were major parts of mainline Elder Scrolls titles but have been absent from the MMORPG.
Firor also mentioned miscellaneous improvements to ESO with controller support for the PC version, subtitles, and a better Group Finder that matches players regardless of their faction which will quicken the wait time for dungeons.