With Rebirth #1, we know that a "JSA' existed and so far two members have made an appearance that include Doctor Fate (Kent Nelson) and Johnny Thunder, including a link to T-Bolt.
We also know from the Rebirth promotional material that DC made reference to Doctor Fate (Kent Nelson), The Flash (Jay Garrick), Dr. Mid-nite (Charles McNider) and Hourman (Rex Tyler). Given that, there's probably a GOOD chance that these characters on the Rebirth poster will be involved in JSA REBIRTH!
This infograph, includes potential members from the New 52, DC You and Rebirth...
However who will be the other members? Will it be a classic JSA or something more akin to pre-flashpoint?
Let that speculations begin!