Now, this poster was actually declared non-canon, but upon further questioning, one of the producers revealed that all the characters in the poster will show up....after visiting some other discussion threads, I found a higher quality image and some really plausible ideas
Now, First from left to right, is Wondergirl.......the character designs match
The archer is....Speedy...as in "real" Roy possibly, look at the right arm..... looks like something is attached where a certain stump would have been
Tim Drake....gauntlets and cape give it away
Static!....look closely, the guy is wearing a hood...and it appears to be the brim of a hat sticking out at the top, this is exactly what Static original design looked like, hoodie with a baseball hat
Blue Beetle, the back antenna give it away, although this image is old, his design was probably considered, but updated.
Impulse...you can tell the larger goggles on his face and the floppier, longer hair.
I am just speculating thats who these guys are...perhaps this will be more of the core team