Avatar is definitely NOT DONE! They will be back for another season!!!
They must come back if you understand the Chakras and Elements and what the co-creators were trying to teach.
Book 4: AIR
The Avatar Story is all about the CHAKRAS as taught by Aang's GURU.
The energy travels up the spine starting with Earth in the Root Chakra, then Water in the Second Chakra, then Fire in the Third Chakra, then AIR in the Fourth Chakra.
Therefore, after FIRE, comes AIR.
Book 4 must be about AIR. This is the wonderful HEART CHAKRA and is all about PEACE and LOVE. (AANG & KATARA)
After AIR, then comes AKASHA/ETHER in the Fifth Chakra. AKASHA is the sum total of earth/water/fire/air. AKASHA is the Fifth Element which produces all those below it.
Book 5 must be about AKASHA/ETHER
Books 6/7/8 must be about Mahat (Three Gunas) also known as the Spirital Elements of the 6th, 7th, and 8th Chakras.
To master the super Avatar State Aang must deal with not just the physical elements (earth, water, fire, air) but he must also master the spiritual elements beyond the physical.
Don't worry........Avatar will return...........I promise!!!
ONE!