3 months of pure training and getting to terms with his blade's split personality.
Should he be a hard worker like Naruto, he'd own Gods in a couple of years
Again, he didn't even need to go FG to cut Aizen in half as he did.
Regarding Aizen's crap talk, He described himself as a transcendental being, surpassing both Shinigamis and Hollows.
But to me, his final evolution is clearly Hollow. Plot hole again? (3 holes in the chest that is)