Alex Gansa said Nazir didn't know Quinn, but we don't really know that. Easy enough to change. We don't even know Quinn's real name. He doesn't actually exist to the CIA, so he could easily be a mole or worse. He didn't explode. He didn't kill Brody. Lots to play with for season three.
I tend to think we haven't seen the last of Brody. Doubtful he'll be on at the start of season three, but he'll appear at some point.