To see Dianna first and then to have a big reveal for Wonder Woman at the end would be cool. I think the issue of magic is going to be something that we'll see a lot of in this movie. Based upon MOS, the appearance of magic in this world would be a BIG deal, and I hope they give it adequate explanation.
I also think that we'll get more of Aquaman than we're expecting, since they already gave away the costume. Seems like a lot to give out for just a brief cameo. My first thought is that this could be a movie about these magic worlds colliding with the real world. All of a sudden, regular law and order will get turned upside down as people react to all the new developments. Batman is sort of an extension of that: man's desire to control and defeat the unpredictable circumstances of gods now walking among us.
As such, I hope we see elements of Atlantis and Wonder Woman's home. Seems like that'd make things easier on Justice League follow up as well.
yeah, it will be interesting to see how they handle the issue of magic in this world. if magic and super powered beings were already prevalent in the world of MOS, then the whole idea of Superman being the "first contact" wouldn't be such a big deal ( not to mention Pa Kent's worry that the world wouldn't be ready for Clark ).
Perhaps magic, the Olympian Gods, the Amazons, Atlantis, Trigon, Azarath, etc. were all part of the ancient world and commonplace. But, a great war happened, and a truce/pact was set up that separated the magic realm or realms from the mortal world.
Maybe a magic seal or veil was created that keeps the magic realms separated or hidden from the mortal world.
So, the modern world is largely ignorant of the magic realms. Any magi who live in the mortal world ( such as Zatanna and her dad or Raven ) practice magic in secret, as public display of "real" magic is forbidden according to the ancient pact.
However, the events in MOS with the World Destroyer tearing up the planet breaks that veil or seal. or else it draws the attention of the Gods and magi and they remove the seal themselves. Perhaps Diana is sent as an "ambassador" by the Gods to investigate Superman.
so, now the modern mortal world will become aware of the existence of these magic realms.