The lack of future dlc or expansion is unfortunate, but kinda expected for me. Larian doesn't create dlcs, so I'm fine with it. In actual state we have "at least something we wanted", an offscreen engine fix based on our imagination that she and Tav found new engine in Avernus and save Karlach for good.

This is faaaaaaaar better than when I finished my gameplay when no patch was released so far. (I romancer her and I even was not able to go with her to Avernus). So this whole thread was successful at the end.

Maybe in the future after few more patches we will see a cutscene that she and Tav finished the Avernus mission and they are save and back in Faerun.

But in my opinion I'm almost sure, that according what is or was in the game, the original idea was that her engine was meant to be fixable.