The Clockwork City DLC, in which we are going to meet Sotha Sil, is now officially announced.

How much we will include the Clockwork City into our RP settings remains to be seen. For now, our main concern is that just including it the way other DLCs have been presented to the player ("hey! Psst! Free cookies in Clockwork city!") would remove every single Telvanni wizard from our setting, because they would all move in with Seht.
It's up to you to join the ancient Telvanni sorcerer Divayth Fyr, track down a powerful artifact, and expose a Daedric conspiracy that could forever change the nature of the Clockwork City, the Tribunal, and Tamriel itself.
Highlights (tl, dr):
Two world bosses
Two delves
New motifs and collectibles
...a host of standalone and daily quests that will reward you with new and unique set items, Motif Chapters, collectibles, and more!
New mini-trial
Asylum Sanctorium - three bosses, drops weapons similar to Maelstrom or Master weapons
Transmutation
Lets you alter traits on your dropped gear to traits you have researched. Requires Transmutation crystals, which "You'll be able to earn Transmutation Crystals by completing veteran level content (such as Veteran Mode Dungeons or Trials)."