Yep, I don't mind if they added ending slides ala obsidian rpgs (it wasn't a norm to begin with), or perhaps some after the fact mentions of our previous actions just like the Act 2 finale.
I agree with previous poster that Larian has never made an expansion, but I just keep hoping since it's a DnD game, I hope they approach it like Pathfinder and/or Solasta.
The problem is a universal one with D&D 5e and is centered around "power creep" or more specifically - you just killed a massive Netherbrain with the ability to kill entire worlds, so where do you go from here?
Past level 12 the power levels are just insane, especially with spells in the 7-9th level range being pretty Godlike to the point that any limitation on the characters can be overcome with magic.
It's not impossible mind you, just really difficult if you are being honest. Bg2 did it with severe limitations on spells in the 7-9 range.
Also, the story of Baldur's Gate feels like it is finally wrapped up. The Main divine antagonists are basically toast at this point, they were barley exarchs and every God of every power level and alignment is going to want them dead, probably including AO for what they tried to do.
However, I do think there is an opportunity for Larian to build out some smaller, more self-contained adventures for the multiplayer market and to write a story that takes place in an entirely new environment/locale.
Personally, I am hoping to see someone return us to Sigil, the City of Doors (Planescape) - I don't think any studio except for Larian has the writing chops at this point to handle that.
AND, Planescape would allow them to feasibly go past level 12 and still provide significant challenges, since Sigil is full of "entities" whose power levels are on par with being Godlike.
since they have managed to make every RPG great. 
