I'll assume at least the Society got a toe grip in every Clan, some rooted, Falcons, some withered, Shark/Fox, but others are isolated cells, quietly alone and not making waves.
What's stopping a new cell from completing the ultimate Society goal(s)?
And assumes they're a dead end, never to be seen again?
Several factions have been redeemed and resurrected before.
Niops, Mica, RWR (Escape from Castle Wulfensteiner) and the hints dropped in the various ISP books.
I know Wulfensteiner is Non-Canon, but the idea of a "dead" faction's lost outpost is still a valid idea.
Every once in a while, CGL drops subtle hints, like bread crumbs, not obvious enough, cryptic almost, but they're there.
Still missing : two "Hidden" worlds, not yet discovered. Several major WoB units disappeared completely en masse. And a few other oddities, here and there..
TT