This image seems to indicate the full JLA lineup come September. On the left, from the top down, we have Deadman, Atom, Element Woman and Firestorm (just one Firestorm, so I'm hoping that the dual Firestorms on the cover of his/their own title is just symbolic). On the right, from top to bottom, we have Green Arrow, Hawkman, Black Canary (maybe) and Mera.
Element Woman may or may not be a new character. Here we have her design and she apparently has the power to "control elements." Uh huh. That should have been obvious. Firestorm can already transmute elements, so I'm not sure how this new character brings anything new to the table.
Actually, I'm not sure she is a new character. Back in the Silver Age, there was briefly an Element Girl who was a feminized version of Metamorpho and had his same power set, the ability to turn her body into any element. But I don't know if Element Woman is an update of this character (she LOOKS very similar) or someone completely new. (Also, why not just use Metamorpho? He's really not that big a character that he needs a female doppelganger!)
As for Black Canary, she very clearly looks like Black Canary... the real Black Canary, that is, not the updated one on the Birds of Prey cover, leading some to speculate that this isn't her. I still think it is, though.
Overall, it's a pretty basic and classic lineup. Cyborg, Deadman, Element Woman and Mera are the only "non-classic" JLA members. Mera's presence isn't that surprising, since she's grown in popularity so much in the last couple of years. And lest you think she's redundant with Aquaman on the team, keep in mind she has a completely different power set (the power to manipulate water) and also, Hawkman and Hawkwoman were on the team together for years! Hell, Hal Jordan and John Stewart have both been active on the team at the same time!
File this under the FUUUUUUUUUUUUCK File. DC has killed off Donna Troy AGAIN!!! By her nature, she'll probably come back... AGAIN, but geez! Come on!
EDIT/UPDATE: I've read speculation that the character I referred to as Black Canary is actually either Power Girl (she DOES seem to have short hair, now that I look closer) or Zealot from WildCATS (she DOES seem to have white hair, plus fellow CATS Grifter and Voodoo are getting their own books, so it's not inconceivable.) With Power Girl... good for her, I guess, but when you already have Superman and Wonder Woman on the team, it's hard to see what niche she'll fill. And if it's Zealot, once again, warrior woman with a sword... you already have Wonder Woman who sometimes uses a sword, so what makes Zealot useful? (Also, you know which CAT I was partial to? Void! I wonder what's up with her.)