It has been established the members died to the last, fighting the Scorch, even if only to delay the inevitable. As I said, it is up to future content to prove that the Residents will rebuild the chapter. To say this is the current status of the faction, when there is no indication this has been done, is speculation. The ABoS are dead until future content chooses to revive them.

^As of 2103, they aren't. Fallout 76 established that.

Established where?

It is not required to complete the main questline. You can, without making use of any exploits, progress through without the BoS.

And you have not provided proof of a surviving, rebuilt Brotherhood with which one might be able to join, and what the Residents might do, does not establish anything. To extrapolate the BoS is rebuilt from this is speculation. As of right now, travel to any location in Appalachia held by the Brotherhood, and all you will find is corpses. The ABoS died fighting the Scorch, and unless resurrected in earnest through future content, it stays dead.

The campaign makes quite the distinction that the faction died fighting to the last. For the case to be otherwise and for it to continue existing, implies that the Residents rebuild the faction. Since we have no evidence to support this claim, the status quo (a dead ABoS) is maintained until expanded on or clarified in future content.

I only like the Outcasts and New Vegas with Elder McNamara.

Three words: Chicago Sentient Deathclaws