That other race (can't recall the name) moved into their own world. Their arrogance allowed the G'ould to wipe them out, although their might be a few survivors somewhere in theory.
That's right - one of the episodes on their home world was where Jack faked stealing some of their technology in order to infiltrate the rogue group with the second Stargate.
Guess if they lost to the G'ould, they wouldn't be much help against the Ori.