Okay, so here's a theory that my gf and I came up with while watching Man of Steel this weekend: Supergirl will be Wonder Woman in the DC Cinematic universe. Or possibly Hippolyta. Consider the science fiction-y vibe of Man of Steel combined with the rest of the potential Justice League: Batman, Green Lantern, Flash, Martian Manhunter, Cyborg....all very science fiction-y characters. It seems unlikely that they would then say "Oh yeah, there's also this island made by the Greek gods and stuff." Now that's not to say there won't be a Themyscira, but they could easily take a cue from the Thor movies and remove the magical aspects and replace them with science. Enter Supergirl. It kinda makes perfect sense: Kara Zor-El's scout ship crashes on Earth 20,000 years ago. Rather than being frozen in the ice, what if she's actually been awake that whole time, witnessing and perhaps participating in the rise and fall of civilizations? Eventually she decides to try and rebuild a Kryptonian paradise on an isolated island, but without the Codex, she's forced to resort to various cloning techniques, hence why everyone is female. By the time Kal shows up, she could perhaps have a daughter who she now decides must go to the world of men to obtain the codex. It'd sorta be a clever way to explain Wonder Woman's powers without magic, while at the same time keeping intact the Amazonian culture and history. It would also set up interesting story parallels (WW with her mommy issues and Kal with his daddy issues). In fact they could even go so far as to make Kara Zor-El/Hippolyta a villain (20,000 years of absorbing yellow sunlight?) that would be quite a formidable threat to the entire Justice League. Of course, her true Kryptonian nature will be held back as the big reveal; they'll introduce Wonder Woman/Hippolyta and Themyscira with all the basic elements there, until at one point in one of the movies BOOM! she reveals she's actually Kara Zor-El. Considering the writers and producers have already stated that they set out to 'fix' some of the issues within the Superman mythos, it seems likely they will also try to 'fix' Wonder Woman in a similar way. Tying her into the Supergirl/Kryptonian mythos would accomplish this in a way that allows for a cohesive, integrated universe, with the 20,000 year gap as an ample excuse for all the Greek mythology, Amazonian stuff to still have had time to develop.