The Elder Scrolls Online: Summerset is the next Chapter for the MMO, arriving on May 21st for PC/Mac and June 5th for Xbox One and PlayStation 4. It includes the new zone of Summerset, the largest island of the province.
The cinematic trailer features the long unseen Altmer Hero from the original trailers narrating this one, and Razum-dar, a well-known Khajiit we've met on many previous occasions. Starting in the dense foliage of the island, the trailer pans up to the Hero climbing towards what one can assume is the Crystal Tower under the influence of a large magical beam. We were also given a gameplay trailer which revealed some of the locations and creatures we'll be seeing in Summerset.
The Chapter was previously teased on March 16 (Friday) with a note written by Queen Ayrenn (Seen here on Twitter) that tells of a very important upcoming announcement. Three days later (Mar 19) a blog post and tweet containing the date of the announcement were posted. The official announcement was made on March 21 alongside another blog detailing the different editions of the chapter that can be purchased.