In chapter 6, what parallel is suggested by the fact that Gatsby never gets the inheritance bequeathed to him by Cody?

Also, it might be symbolic for the fact that Gatsby, even though he has acquired a vast fortune, will never be part of the "old, established aristocracy", of the "West Egg society". Even though, after he becomes involved in illegal activities he is wealthy, he will never be accepted by the established society (to which Tom and Daisy belong), who got their money traditionally, namely by inheritance; because he got his money through the "American Dream". This shows the futility of his American Dream, and how even achieving it will not land him the ultimate object of his strife: Daisy.
Even though Gatsby thinks he will inherit Cody's fortune, he never actually does; and even though he thinks he will get Daisy's love by becoming wealthy, he never actually does.