Originally Posted by kael03
Kubo probably hasn't thought that far ahead (as is his writing style to just wing it). But he made Aizen's Shikai completely overpowered so the thought of his bankai would just make someone's head explode. Or it could be so ridiculously retarded Kubo would be shunned from ever writing again.
Or Aizen will turn out to be another Zaraki.
He was soo uber from the start and his shikai was soo uber from the start that he never bothered to learn his bankai as he never needed it.