Okay, so a lot of you guys have been saying that Rohan, Tenzin's youngest, may be an earthbender because of his eyes and his mother's nationality, but that is not the case and here's why:
1: Having green eyes doesn't necessarily mean you're an earthbender. I mean, Rohan could have just gotten it from Pema.
2: Air Nomads are always airbenders and always have airbending descendants due to the high spirituality rate of their element. There is no exception to this rule.
2. Aang had three children, and only one is an airbender. Kya is a waterbender, and Bumi is a nonbender. So, I guess there are, in fact, possible exceptions to that rule.
If Pema were an Air Nomad, (which she isn't), this might be the case. You have to be an airbender to be an Air Nomad, but if someone is born into an airbending family a nonbender, they're just a nomad. Yes, all Air Nomads are
airbenders. But if what you are saying is the case, then all of Aang's kids would be airbenders.
However. Pema could have any type of bending or nonbending child, because we don't know her parentage. What genes are at work here? We don't know. But I'm assuming, to draw attention away from the new baby and back to Korra, the baby will be either an airbender or nonbender.