well the only Larian game for the Divinity serie was Flames of Vengeance and it added aleroth to the previous game (which was originally planned for the basic game but had to be cancelled as Larian lacked time...) so IMO, IF Larian makes an extension for D:OS it will be an extention with story content but I am not really sure about a standalone...

Personally, on one hand I'd like to see an extension for D:OS adding the features discussed during the KS campaign (especially the D/N schedule with bonus/malus and the NPC schedule)

and on the other hand I really look forward Divinity 3 where we will FINALLY kill Damian...

"-Oh that's fullmoon, cuttie cuttie sheep
-baaaaaaOOOOORGH"
***Sprotch***

Weresheeps will rule the world (At least one night every 29 days)