Does the ending of the TV Series Avatar: The Last Airbender bother anybody else?

So at the end of Avatar: The Last Airbender, they give ABSOLUTELY NO CLOSURE to the issue of Aang being the last of the air nomads. When Aang dies there will be no more, and the cycle of the Avatar being reincarnated through each of the four elements will be broken. This seems like a pretty big problem to me.