The Joss Whedon web series - which starred Neil Patrick Harris - first debuted online in 2008 and will make its TV debut on The CW on October 9.
"I've heard about [a sequel] for years now," Helberg told Digital Spy. "Yeah, I think everyone is excited to do that."
The Big Bang Theory star - who played Moist in the original Dr Horrible - also joked about Whedon's recent Avengers success.
"Joss did some movie that came out this year - I can't remember," he quipped. "Maybe when he has some time we'll make a billion dollars in opening weekend with Dr Horrible."
Fellow Dr Horrible star Nathan Fillion (Captain Hammer) previously told DS that he expects a sequel to get made eventually.
"Do I think [a sequel is] ever going to happen? Yes, I do," he said. "I would lean more toward yes than no."
> Nathan Fillion on Avengers sequel: 'I'm not famous enough for it'
Watch Nathan Fillion discuss Joss Whedon and Dr Horrible below: