Korra follows after him, turning around and smoothly whispering "Team Avataaaar~" before the door closes behind her. 

I think MAYBE, MAYBE, we save the air case. Due to the staggering lack of air benders I don't think Xana and Xano would want to find someone to carry said power YET, it's too precious. The cases of Water, Fire, and Earth are surprising enough for Tenzin. The fact benders are suffering yet normal civilians are gaining those powers IS notable imo, because it's something that has never in the history of the world occurred. It furthers the hypothesis that someone truly is behind this, that it's not some random epidemic.