Peter David is involved, and Mary Marvel and Secret are both gonna be in it. Yay! ^^
Hm, I wonder if, with the cancellation of Brave and the Bold (Boo!) they'll use this comic as a means to introduce the DCU's teenage characters. So, while BatB had a circulating cast of Batman with the Metal Men or whatever, the Young Justice has the team meeting Wonder Girl, Mary Marvel, Traci 13 etc.
Geoff Johns did say that Cass was going to appear outside of comics soon, that could apply to this show, though I think that it's more likely to be the DCU Online game, which already has her appearence confirmed.
I guess it could be possible that Cass and Steph could appear (Steph especially as she has her Spoiler persona to fall back on), but considering Robin in his show is Dick Grayson for some reason, if a Batgirl was to appear I guess that it'd have to be Babs. *grumble*
Having Dick instead of Tim is kind of weird though, especially as they have Conner, Megan, Cissie etc. on the team (though Impulse may be Wally West).
Anyways, link,
http://robot6.comicbookresources.com/2010/07/sdcc-10-peter-david-writing-episodes-of-young-justice-cartoon/