DaxCordite
There is no garuntee that all of Aang's kids will be Airbenders. If he truely is the last person alive with Air Nation blood in his veigns then he has to interbreed with another Nation. That gives the kid a 50/50 chance of inheriting Air Bending or Water/Eath/Fire Bending. (provided bending is genetic to each people) There's also the possibility of any kids of Aang being non benders. We know from Canon that Non Benders and Benders can show up in the same family. And with each generation the blood would get thinner unless they turned to inbreeding which while it would help sure up the Air bender Genes it'd also eventually lead to other issues Since when you inbreed you double the good genes and the bad genes. So while a few instances of inbreeding won't produce flipepr babies if they have to dit heavily there will be consequences.
That's true - he may not have an airbending child, and that's where other theories would have to come into play. Still, even though they wouldn't multiply fast or anything, but they'd still multiply, as long as at least one of Aang's children is an airbender. And if they were they'd multiply enough over the years to most likely have another Avatar.
All I'm trying to prove is that there is a way that the Avatar cycle wouldn't end after the next firebending Avatar.
