https://forums.bethsoft.com/topic/1417092-hints-found-about-the-next-dlc-found-in-18-beta/
According to several people on the official Bethesda forums, there latest patch for Skyrim included files for the next DLC.
Bonemold, Chitin, Nordic, and Stralhrim armor from Morrowind?
Dragon mounts?
seriously? WHAT WILL BE NEXT?
Also it MIGHT be called Dragonborn
https://forums.bethsoft.com/topic/1417057-time-for-some-spoilers-form-the-latest-beta/
http://tsdr.uspto.gov/#caseNumber=85626061&caseType=SERIAL_NO&searchType=statusSearch
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UPDATES
https://forums.bethsoft.com/topic/1417456-18-beta-update-solsthiem-dlc-hints-thread-10/
According to several people on the official Bethesda forums, there latest patch for Skyrim included files for the next DLC.
DLC for PS3?data\interface\Translate_english.txt
$Crafting_$DLC2ArmorBonemold BONEMOLD
$Crafting_$DLC2ArmorChitin CHITIN
$Crafting_$DLC2ArmorNordic NORDIC
$Crafting_$DLC2ArmorStalhrim STALHRIM
$Dragonborn Quests Completed Dragonborn Quests Completed
$DRAGONBORN_ESMName Dragonborn
$DOWNLOADABLE CONTENT_PS3 DOWNLOADABLE CONTENT
update.bsa\interface\exported\hudmenu.gfx & quest_journal.gfx
Hudmenu compass markers/quest journal quest header:
http://i.imgur.com/mWGUj.png
update.bsa\interface\startmenu.swf\startmenu.as:
MainList.entryList.push({text: "$DOWNLOADABLE CONTENT" + (iPlatform == 3 ? "_PS3" : ""), index: StartMenu.DLC_INDEX, disabled: false});
Update.bsa\meshes\animationsetdatasinglefile.txt
DragonMountedDualMagic.txt
DragonMountedDualStaff.txt
DragonMountedMLhSolo.txt
DragonMountedMLhStaff.txt
DragonMountedMRhSolo.txt
DragonMountedMRhSolo_ShieldOrTorch.txt
DragonMountedMRhStaff.txt
Bonemold, Chitin, Nordic, and Stralhrim armor from Morrowind?
Dragon mounts?
seriously? WHAT WILL BE NEXT?
Also it MIGHT be called Dragonborn
https://forums.bethsoft.com/topic/1417057-time-for-some-spoilers-form-the-latest-beta/
http://tsdr.uspto.gov/#caseNumber=85626061&caseType=SERIAL_NO&searchType=statusSearch
.
.
.
UPDATES
https://forums.bethsoft.com/topic/1417456-18-beta-update-solsthiem-dlc-hints-thread-10/
Gameplay Additions :
Spears
Dragon Riding
Mounted Magic
"Boat Riding"
Use of some spells and shouts while Dragon riding
Tree and ground ambushes
New armor types :
Chitin, Bonemold, Nordic, Stalhrim, all being both light and heavy
New places:
Places on Solstheim, namely standing stones, Castle Karstaag, Raven Rock
A Telvanni Tower
Some place called "Miraak Temple"
The repeated mention of something "Benthic" suggests some (deep) underwater area
Apocrypha
New creatures:
A "Benthic Lurker"
Some daedric creature related to HM (Hermaeus Mora or Herma-Mora?)
Scribs (and thus probably Kwamas?)
Netches
Rieklins
Boars
Dwemer Ballistae
Something with tentacles
(Since there are light chitin armors, I wouldn't be astonished if the Shalk came back)
Something involving a heart ripped off. (Something related to Briarheartss maybe? Or to Pelinal? Or something Lorkhan-esque)
The DLC title is presumed to be "Dragonborn".
As Bigbossbalrog said, the mention of a Chieftain hints at a return of the Skaals.