Are the humans who were at the wedding already back in Brethil during the hunt for the wolf? If we have the wolf news come in to crash the wedding party, we’d need to create a ‘safe space’ for the humans to return to their homes before Carcharoth gets near to Brethil. One possibility could be that the news of the wolf comes while Carcharoth is still at some distance from Doriath/Brethil - but heading in their direction. From memory, the hunt for the wolf only kicks into gear when Carcharoth penetrates the Girdle. There can be some time between the news of the Wolf and the imminent danger he poses (plus the Thingol’s guilt feelings that it was the Quest for the Silmaril that wrought this danger, and BEren’s sense that the quest has not been achieved yet while Carcharoth still has the Silmaril) I can imagine that the humans at the wedding would want to get home safely and quickly and be with their loved ones back in Brethil rather than stay indefinitely in Doriath.Emeldir et al leaving Brethil will be an Episode 13 storyline, specifically setting up things we need for Season 7. In Episode 12, those who visited Doriath for the wedding will be returning to Brethil.
I imagine that episode 12 will end with Beren's death and farewell to Lúthien. So, Lúthien's death will be a matter for Episode 13.
As for timeline beyond Season 6, that is not within the scope of this thread.