This was cross-posted to the NIN facebook page. No details on who is appearing but given previous appearances it's plausible TR & AR may be participating.

Comic Con Watchmen Panel blurb:

Set in an alternate history where masked vigilantes are treated as outlaws, HBO’s upcoming series Watchmen embraces the nostalgia of the original groundbreaking graphic novel of the same name while breaking new ground of its own. From the co-creator of The Leftovers, Damon Lindelof’s new series is set in contemporary 2019 where roughly 30 years have passed since the original Watchmen story. Please join producers and series stars for an exclusive sneak peek of the first episode of the HBO series followed by a panel discussion.
Comic Con Page