Updated:

No upcoming DLC / Add-on / Expansion has been announced so far but there is a decent chance that D:OS 2's loose story ties will come to a conclusion with additional content.

Speculations

  • Malady's request about her pact was never revealed despite being hinted at all game long.
  • The God King is still undefeated.
  • One of the ending slides shows a map with new locations north of Arx:
Map that shows the regions north of Arx

Map that shows the regions north of Arx

  • Names of the Regions:
    • Beckonbridge Castle
    • Void Tainted Ancestor Tree
    • Black Ring Ruins
    • Atraxia
    • The Deathfog
    • Deadlands
    • The Holy Mountain
    •  Montagan's Rest


Comments by Larian Studios[1]

You've mentioned the patch, however what does Larian have planned in the long run for Divinity: Original Sin 2?
We have a couple of things that are in the works but we'll only announce them when we're ready. There's stuff coming, for sure. 
 
To that end: It's early days yet, but I assume the success of number two means we're in line for a Divinity: Original Sin 3, 4 and 5? 

[Laughs] We have a couple of surprises planned. But we're going to work on the patch just now, then we're going to work in silence for a little bit so that we can get our shit together and then… yeah, I'm pretty sure there will be at least one big surprise in there.

 

References

 
  1. ^ http://www.pcgamer.com/swen-vincke-on-the-future-of-divinity-original-sin-2-and-the-pros-and-cons-of-open-development/