Most of the boxers who talk trash usually have proven themselves on some level of sorts. Khan really hasn't so he comes off as extremely arrogant and lost. I think being somewhat tied to Frank Warren (the Satan of British boxing) doesn't help his case either.
i think he will win a world title even with his chin, and he's a big lad for a lightweight, his chin may improve if he moves up a weight (although they hit that much harder).
Khan has fast hands and decent power but his chin will let him down again soon, im 100% sure of that.