Batman's The Flying Fox in the Justice League Comic-Con trailer featured a green light leading to speculation it may be Green Lantern, and some sort of hologram in a Bruce Wayne scene was also thought to be Supergirl:
Now with the release of today's Justice League trailer, it seems pretty clear that those are not references to either Green Lantern or Supergirl.
Regarding the thought of Supergirl in the Justice League trailer, the hologram(?) is again shown with Bruce Wayne stating, "The world needs Superman." I'm not sure why Superman's legs look the way they do, but that does seem to be Superman's cape as well.
For Green Lantern, as pretty much thought the green lights are just that, and not Green Lantern, as today's footage offered a better look at The Flying Fox:
Now that doesn't necessarily mean Green Lantern and Supergirl are not in the Justice League movie, as there have been rumors about Green Lantern, and Man of Steel paved the way for Supergirl in the DCEU, so it's still a possibility. I would say there is more of a chance of Green Lantern appearing as the Green Lantern Corps movie is being developed, and Green Lantern is a founding Justice League member. I would guess if there is anything about Supergirl, it would again be sort of an Easter Egg, perhaps similar to Man of Steel, rather than a full blown cameo role.
Justice League has a November 17, 2017 release directed by Zack Snyder, with the story by Chris Terrio and Zack Snyder, the screenplay by Chris Terrio and Joss Whedon, and stars Ben Affleck as Batman, Henry Cavill as Superman, Gal Gadot as Wonder Woman, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, J.K. Simmons as Commissioner Gordon and Willem Dafoe an Atlantean, Nuidis Vulko.
Fueled by his restored faith in humanity and inspired by Superman’s selfless act, Bruce Wayne enlists the help of his newfound ally, Diana Prince, to face an even greater enemy. Together, Batman and Wonder Woman work quickly to find and recruit a team of metahumans to stand against this newly awakened threat. But despite the formation of this unprecedented league of heroes—Batman, Wonder Woman, Aquaman, Cyborg and The Flash—it may already be too late to save the planet from an assault of catastrophic proportions.