It'll probably be for any number of reasons, most of which we'll never hear about. I've heard that the focus groups didn't go well, but why is that? Did they group just think "comic book characters in stupid looking costumes are stupid"?However, if the Kelley pilot does get rejected, I'm hoping NBC (and more importantly, Warner Bros.) won't blame it on the concept/character of Wonder Woman. I'm hoping they'll realize that it could've worked better in different hands, and maybe try to develop a new version.
In which case, it could have been the comic book nature of the character that got it rejected (or that will be the assumption), and then comic book characters will be on the outs and not just Wonder Woman but comic book characters in general will be avoided for TV development.