So... Here's everything we know so far:
- According to R.A. Salvatore's latest Drizzt book, Hero, Acererak and his Tomb are now located in Chult (a region of the Forgotten Realms). In Hero, the main villain reveals that Acererak is distributing mirrors with green-devil frames in order to harvest souls throughout Faerun.
- The next adventure path will feature Artus Cimber and the Ring of Winter, as revealed in Storm King's Thunder. Chris Perkins confirmed in a tweet that Artus and the Ring would feature in a 2017 product. Artus, coincidentally, first appeared in a Forgotten Realms novel set in Chult. Source: https://twitter.com/ChrisPerkinsDnD/status/799801288242262016
- The last Acquisitions, Inc. game, hosted by Chris Perkins, ended with the party being guided to Chult. In answer to one of the party's questions, an Oracle told them to "Look for a lost city in a distant land. Let the children of Ubtao guide you." In the current storyline, something called the "soulmonger" is trapping souls (much like Acererak). "The evil that is trapping souls is drawing life from those who have been raised from the dead. They too will be consumed. The soulmonger must be destroyed."
- Maps of Chult were recently uploaded to the Adventurers League media folder.
- In the city of Mezro (in Chult), "Small dinosaurs are not uncommon in the city, as they are often used for beasts of burden and as mounts by some of Mezro's more adventurous folk" (The Jungles of Chult, p. 12). That could very well be Mezro in the teaser image.
Plus, the name of the stream, "Stream of Annihilation" is a reference to
spheres of annihilation, and the image is a green-devil face, both of which feature heavily in
Tomb of Horrors. So I think we can confirm at this point that the adventure is a
Tomb of Horrors sequel set in Chult.
To quote myself in a previous thread, I "predict that Acererak and his dungeon will have less of a presence in the new adventure than Strahd had in
Curse of Strahd. In other words, most of the adventure will feature new locations and dungeons, all leading up to an epic battle with the lich himself. I also predict that there will be some planar or dimensional travel involved, due to Artus's role as an Exarch of Auril and Acererak's journey between worlds."