The Eliminati were a group of Vampires. A duellist cult, they were acolytes of the demon Balthazar. Balthazar was severely weakened, and the Eliminati tried to restore him to full strength. Buffy put a stop to their plans, killing The Eliminati and Balthazar.
It would seem that all The Eliminati were killed, but it is possible a few survived.
These guys were neat because they used swords, and prided themselves on it. They also showed that Vampires will sometimes form groups and work for other Demons. Something more then just kill and eat. I'm unsure how old these guys were, it's hard to say. They could be as old as the cult itself, or they could be new to it.