"Until the big bad comes knocking on the door, and we have to fight anyway."

It follows on neatly at the end of her statement. Her opinion of the circles coming for Rifters might be just that, an opinion, but from what Richard knew of Corypheus, it was way more of a certainty. He tips his head slightly.

"I get it. You're trying to give us an out. It's a nice thought."

But Seth was already going to be looking for excuses, high and low, just like he had with Amaru. And just like with Amaru, there didn't really look to be a reliable, long-term exit from the potential consequences of things going sideways. So: better to stick around. Make sure they didn't go sideways.