Patch 3 comes out on the 21st, it probably won't have a good Karlach ending since that would be kinda soon and they already said they're working on adding epilogues to all of the characters. Beyond that they haven't said what they're going to do, but since the most requested story change after epilogues is giving Karlach a good ending (I checked), I have high hopes that will be next.
Also I have a post on the discord feedback thread asking for another Community Update to address Karlach having a good ending (among other things) and it's pretty highly rated, so hopefully they will take note and maybe give us a peek behind the curtain.
