Rorschach Is Malcolm Long's Son In Doomsday Clock... But Not On HBO
Since the release of the original Watchmen limited series, there have been two follow-up series published by DC Comics: a prequel series called Before Watchmen, and a sequel series called Doomsday Clock. The latter series, like HBO's Watchmen TV show, featured a successor to the mantle of Rorschach: Reggie Long, son of Malcolm Long, the psychiatrist who evaluated Walter Kovacs during his time in jail. Reggie was institutionalized following the devastation in New York City, but escaped with the help of former vigilante superhero Mothman, who gave Reggie the Rorschach mask as a parting gift. Thereafter, Reggie took up Rorschach's name and signature look.
While it might seem obvious to look for clues to HBO's Watchmen sequel in the other Watchmen sequel, it's safe to say that Reggie Long definitely won't be Rorschach in the TV show. In his open letter outlining his general vision for the series, Damon Lindelof wrote that "this new story must be original. It has to vibrate with the seismic unpredictability of its own tectonic plates." That's an elaborate way of saying that no, the show won't be based on Doomsday Clock - not least because it was in development before Doomsday Clock #4 (which explored Reggie Long's backstory and how he became Rorschach) was even published.
If we had to guess (and for now, that's all we can do), it seems most likely that the new Rorschach is an original character. While it's possible that this is someone we've met before - perhaps an elderly Dan Dreiberg paying tribute to his old sort-of friend - or the offspring of one of the original Watchmen characters, Lindelof has said that his goal with the show is to create something fresh and new. It would be difficult to do that if every character in HBO's series was either a character from the original graphic novel, or somehow connected to them.
Set photos have revealed that, after thirty years, the masked heroes from Watchmen have gained a kind of legendary status, and are the subject of a TV show called American Hero Story: Minutemen. With that in mind, it's likely that this Rorschach is someone who idolized the first Rorschach after seeing him in newspapers and documentaries, and researching online. That would certainly fit with the fact that the Rorschach mask we see in the teaser footage seems like a cheap, homemade knockoff.
There's also the question of whether this new Rorschach will be a "good guy" or a "bad guy" - even though things are rarely so simple in the world of Watchmen. The original Rorschach was flawed to say the least, but is generally considered to be on the side of heroes, and stuck to his principles so resolutely that he was ultimately willing to die rather than betray them. If this new Rorschach does indeed idolize the first, it makes sense that they would want to take up his legacy of belief in a black-and-white morality - but even that could be interpreted in some dangerous ways.