Now in the upcoming wave expected to be released June 2nd, we get Ork, Space Marine, and Necrons flyers. That leaves a lot of codices available for a second wave. Tyranids, Chaos Marines, Dark Eldar, and Eldar would probably fill out the 2nd wave. (Tau would more than likely be first of 2013 alongside their new shiney codex).
Please remember that these are rumors
Multiple birdies have mentioned sightings of an Eldar flyer though. "In the warehouse", make of that what you will.
There is supposed to be a second flyer wave later in the year, it isn't beyond the realms of possibility that we will see an Eldar flyer then with WD rules like the incoming batch are presumed to have.