Existing GB members select new GB members.
Since numbers of anointed have been going up they'll likely not run out of anointed brothers to choose any time soon. They may however abandon the literal 144.000 teaching if the number keeps going up, or forbid new anointed, or just not count them. Who knows what they'll come up with next. Never in a million years would I have predicted the overlapping generation nonsense. They could come up with anything and see if it fly.
They seem to have lost their way on teachings. They appear to have lost any semblance of coherence or credibility. Or is that just my impression?